Talk:Paper - The fontanella metopica and its remnants in an adult skull (1918)
THE FONTANELLA METOPICA AND ITS REMNANTS IN AN ADULT SKULL
ADOLF H. SCHULTZ
Carnegie Institution of Washington
FIVE FIGURES
It is not uncommon to find in the skull of a newborn infant a small fontanelle between the two frontalia in their nasal third. This is usually called fontanella metopica (f. medio-frontalis, fonticulus interfrontalis inferior) (fig. 1). A considerable number of skulls, both of children and of adults, showing short, irregular, transverse or V shaped sutures or fissures in the midline of the frontal bone above the level of the superciliary ridges have been described in the literature and interpreted as remnants of the fontanella metopica. The author has found in the skull of an adult an abnormal suture, which is comparable to those above mentioned, but which is more extensive than in any of the cases previously described; accordingly its publication appears justifiable. This specimen (fig. 2) belongs to the Anatomical Department of the Johns Hopkins Medical School and w^as kindly placed at my disposal by Dr. W. H. Lewis.
The skull is that of an American negro, fifty-five years of age. It might be mentioned that the skin over the frontal region was absolutely normal, therefore any external factor, whether accidental or surgical (trepanation) can be excluded as the cause of the anomaly. The greatest length of the skull is 193 mm., the greatest breadth 148 mm., the basion-bregma height 128 mm. and the horizontal circumference 553 mm. The weight of the skull, including the mandible, is 985 grams, a figure, which is close to the upper limit of variation of weight for the human skull. This is an indication of the thickness of the bones of the skull, which is characteristic of the negro. Most of the sutures are
259
260
ADOLF H, SCHULTZ
Fig. 1 Frontal view of the skull of a male negro fetus with a fontanella metopica.
Fig. 2 Frontal view of the skull of a negro with an abnormal suture on the frontal bone.
FONTANELLA METOPICA IN AN ADULT SKULL 261
obliterated, on the inner surface more than on the outer. This is also true of the internasal suture, although its course can still be recognized (the suture was retouched in fig. 2), and therefore the right nasal bone is found at its upper end to extend far into the left. On each side, at the incisura parietalis, there is a Wormian bone. The lambdoid suture is rich in Wormian bones. It is noteworthy that there is present on both sides of the mandible a well pronounced processus anguli mandibulae (apophysis lemurica) , which points downward and outward and shows rough outhnes for muscle-insertion. The latter are likewise present on the thick zygomatic arch. Attention may also be called at this point to the prominent processus marginalis on the posterior border of the malar bone. The processus anguli mandibulae assumes in our case special interest, in as much as Herpin ('07) reported that this anomaly is rare in the negro and when present is poorly developed.
The abnormal suture on the frontal bone, which is situated not exactly median but somewhat to the right, consists on its outer surface of a transverse, irregular, dentate part, 15 mm. long, and of two lateral, ascending limbs, which diverge upward and have a length of 9 and of 13 mm. on the right and on the left respectively. The distance between the upper ends of these diverging limbs is 23 mm. The middle of the transverse part is situated 25 mm. above the nasion and 15 mm. below the line connecting the two tubera frontalia. If, as according to Schwalbe ('01) the length of the frontal arc is represented as 100, then the transverse portion of the suture lies 20.3 above the nasion. It is of interest to compare the position of the abnormal suture on the frontal bone in the author's case with those reported by Schwalbe ('01), Fischer ('02) and Davida ('14). Table 1 is a compilation of the tables of the two first mentioned authors with the corresponding measurements of Davida's case and of that herein described. The figures show that the suture or fissure is always situated below the level of the tubera frontalia, and with only two exceptions always in the upper half of the nasal third of the nasion-bregma arc. In the twelve European skulls the average relative distance between the nasion and the
262
ADOLF H. SCHULTZ
TABLE 1 Position of the transverse abnormal suture on the frontal hone of adults
DISTANCE
POSITION
OF THE SUTURE
OF THE SUTURE
FROM NASION
BELOW '
AUTHOR
RACE
AGE
SEX
IN PER CENT OF
THE FRONTAL
ARC
INTERTUBERAli
LINE IN
MILLIMETERS
r
European
32 y.
cf
18.5
17.5
European
ad.
d"
17.3
11.0
Schwalbe ■
European
31 y.
d'
17.1
19.0
European
58 y.
d"
20.3
19.5
European
41 y.
&
13.8
20.0
European
ad.
&
18.0
18.0
European
64 y.
d"
23.9
19.0
European
40 y.
d"
22.2
20.0
European
ad.
d'
18.5
16.0
Fischer
European
ad.
?
18.2
15.0
"
European
41 y.
9
20.0
29.0
European
19 y.
9
17.4
16.0
Negro
ad.
c?
27.5
12.0
Negro
ad.
d"
21.8
11.0
Davida
?
Negro
50 y. 55 y.
?
d"
15.4 20.3
Schultz
15.0
suture is 18.8 mm., and the distance between the intertuberal Hne and the suture 18.3 mm. The average of the two negro skulls of Fischer and that of the author's case is, for the corresponding measurements, 23.2 and 12.6 mm. respectively. Therefore the suture in the negro seems to be relatively higher above the nasion and closer to the intertuberal line than in the white. The exact determination of the position of this abnormal suture is also of importance in the explanation of its origin, as will be seen later.
Upon examining the inner surface of the skull, the suture is likewise found to be extensive (fig. 3). Incidentally it might be stated that the crista frontalis interna is only moderately developed, as was the case in the skull with the same anomaly described by Rauber ('03). In two of Schwalbe's cases the crista frontalis was examined, and found in both to be broad and blunt. For the most part the abnormal suture on the inner surface communicates with that on the outer surface, often allowing the passage
FONTANELLA METOPICA IN AN ADULT SKULL
263
of a fine bristle. The transverse portion presents itself on the inner surface as eight short perpendicular adjacent fissures, with a total width of 9 mm. and located 19 mm. above the foramen coecum. The lateral hmbs of the suture, which also diverge upward, are straight regular fissures, in contrast to those on the tabula externa. The right limb is 13, the left 19 mm. in length and they are 16 mm. apart at their upper ends. The bony part included by the suture is narrower but higher on its inner side than on the outer. On a horizontal section through the frontal
Fig. 3 Frontal bone of the skull in tigure 2 seen from the inside (upper part sawed off).
bone, at a level somewhat above the transverse portion of the abnormal suture, a trapezium is formed by the lateral limbs, with its shorter base directed inward. This wedge-shaped piece of bone is plainly shown in Rauber's section of a similar case.
Schwalbe directed attention to the fact that adult skulls showing remnants of a fontanella metopica present an unusually large interorbital breadth. Table 2 is a compilation of tables by Schwalbe and Fischer with Rauber's case and that of the author, in which the interorbital breadths and the interorbital indices are given. The interorbital index represents the relation between the interorbital breadth and the internal biorbital
264
ADOLF H. SCHULTZ
TABLE 2
Inlcrorhital breadth and interorhital index on adult skulls ivith the abnormal suture or fissure on the frontal bone
AUTHOR
RACE
SEX
IXTERORBITAL BREADTH
IXTERORBITAL INDEX
Schwalbe \
[
Fischer •
Rauber
European European European European European
European
European
European
European
European
Negro
Negro
European
Negro
& d' d" d'
& d" d' 9 9 d' d" & d"
m m .
28.5 32.0 27.5 28.0 31.0
31.0 29.0 29.0 24.0 30.0 26.0 37.0 30.5 32.0
26.6 30.2 27.5 26.4 29.8
30.1 26.9 26.6 25.8 29.4 26.3 33.3
Schultz
29.1
breadth; the technique of these measurements may be found in Schwalbe's studies on Pithecanthropus erectus ('99). In this same work are pubhshed similar measurements of a considerable number of normal skulls of most heterogeneous races. According to these measurements, the interorbital breadth varies between 18 and 31 mm. with an average of 24.2 mm., the interorbital index lies between 20 and 30.1 with an average of 24.3. A comparison of these figures with table 2 shows that both the absolute and relative interorbital breadths of skulls showing remnants of a metopical fontanelle are much above the average.
For the determination of the relative frequency of the anomaly in the two sexes, the material at our disposal has been much enlarged through the published cases of transverse fissures in the frontal bone of children and newborns. In Schwalbe's cases sex is stated in 9 juvenile and in 5 adult; all were male except one newborn. Fischer found in 1 newborn and in 7 adults, in which sex was known, that the female sex was represented twice.
FONTANELLA METOPICA IN AN ADULT SKULL 265
Adding to these the case of Rauber and that of the author, both of which were males, the total of males is 21, of females 3. The anomaly, therefore, would appear to be of much greater frequency in males. This same preponderance has been found by the author ('16) in another anomaly, namely, the persistent canalis cranio pharyngeus, and this relatively greater frequency has been likewise shown in respect to other anomalies. From this it would seem probable that anomalies are more common in the male, but whether this is a rule for progressive or for atavistic anomalies, or for both, can only be determined when care is taken by investigators to always mention the sex in reporting anomalies.
Short transverse sutures or fissures occurring in the lower third of the frontal arc in adults have always been interpreted by the various authors as remnants of the fontanella metopica, but the origin of the latter has been explained in widely different ways. The metopic fontanelle was first described by Gerdy in 1837. He was followed by Hamy and the Italian scientists Maggi, Riccardi, Staderini and Zanotti. Of these, Hamy ('72) sees in the metopical fontanelle a divergence of the lines of ossification of the tubera frontalia. Maggi ('94, '98, '99) interprets the fontanella metopica as a product of the approximation of the four frontalia media. These assumptions are based upon his isolated comparative anatomical observations. Zanotti ('01) explains the medio-frontal fontanelle as the last trace of the foramen, which corresponds to the location of the paraphysis in primitive vertebrates; in other words, a foramen frontale for the paraphysis similar to the foramen parietale for the epiphysis. Both Maggi and Zanotti to a certain extent place atavistic interpretations upon the fontanelle, but these must be considered as extremely hypothetical.
Bolk ('11) w^as led to believe that the fontanella metopica arises at the site of the primitive or primary nasofrontal suture. This opinion was based upon observations on monkeys, in which the nasal bones have become shortened, that is the supramaxillary portion of the nasalia is displaced by a medial growth of the frontalia, by which process a secondary naso-frontal suture, situated closer to the apertura nasalis, is formed. This theory
266 ADOLF H. SCHULTZ
does not explain in a satisfactory manner the extremely rare occurrence of a true metopic fontanelle in monkeys, together with the relatively frequent appearance of incomplete nasal reduction. On the other hand, the relative frequency of the metopic fontanelle in man according to Schwalbe is 15.2 per cent in children up to 1| years, whereas high reaching nasal bones, such as are found in monkeys, have never been described in the human skull. Moreover, it must be borne in mind that the remnants of the fontanella metopica are often situated in the adult high above the nasion. As shown in table 1 , the lowest point of the remnants of the fontanelle is located as much as 27.5 per cent of the frontal arc above the nasion, its middle point, being even higher. If the fontanelle reallj^ corresponds to the original uppermost end of the nasalia, then the latter must have extended between the frontalia high above the orbits and the supercihary ridges. Bolk assumes that the supranasal portion of the frontal suture (supranasal field or triangle) — a frequent finding in adults — is the result of the reduction of the nasaha. However, this supranasal suture reaches as a rule only shghtly above the glabella and not, as Bolk supposes, to the level at which the fontanella metopica occurs.
Rauber ('06) describes the skull of a child with two fontanelles at the frontal suture (fonticulus interfrontalis superior et inferior) which in his opinion had become separated from the frontal arm of the anterior fontanelle. The fonticulus interfrontahs inferior corresponds to the metopic fontanelle, and as a factor in its remaining patent Rauber considers it possible that the site of the anterior neuropore of the medullary canal of vertebrates exerts its influence under special circumstances, even to the ossification of the skull.
Schwalbe ('01) in contrast to the explanations offered by previous authors, considers it possible that the metopic fontanelle is to be conceived as a progressive variation, which bears a relation to the greater development of the frontal lobe of the cerebrum. The adult skull described in this paper would seem to support this theory inasmuch as its capacity was 1520 cc. and its smallest frontal width was 109 mm. Both these measurements are rather large for the negro; on the other hand Fischer's cases
FONTANELLA METOPICA IN AN ADULT SKULL 267
showed the metopic fontanelle to be present in two idiots, one of them a microcephahis with a skull capacity of only 704 cc. Schwalbe in his explanation makes use of the hypothetical supposition that the tubera frontalia might consist of two adjacent ossification centers, which usually join immediately, but in exceptional cases remain separate, later forming two independent systems of lines of ossification. The divergence of these lines forms the metopic fontanelle, which in children is situated on a plane with the tubera frontalia. Schwalbe emphasizes the fact that the metopic fontanelle and its derivatives are always found at a definite location, while the fontanelles and fontanelle bones which are found at times in the upper portion of the frontal suture have a more variable situation and are to be included in the great fontanelle. Schwalbe cites among other the cases described by Staderini, in which the fontanella metopica is connected with the great fontanelle by a wide space. In spite of this, however, he makes a distinction between the two above mentioned fontanelles, which rests purely upon the situation of the metopic fontanelle. According to Schwalbe in children up to 13 months the latter varies in respect to the lower end of the fontanelle from 5.6 to 17.8, in respect to its middle point from 11.2 to 22 per cent of the frontal arc above the nasion. Fischer described the skulls of two children in which interfrontal fontanelle bones are divided in two and in three partfe respectively. In one of these the middle point of the fontanelle bone was situated 30.6 in the other 50 per cent of the frontal arc above the nasion.
It is evident that the position of the metopic fontanelle is not as definite as claimed by Schwalbe, who makes the following statement :
In the rare cases in which two or even three groups of Wormian bones occur in the frontal suture, only the lowest corresponds to the normal medio-frontal fontanelle; those situated near the parietal bones, however, are to be considered as Wormian bones in an abnormally wide suture (hydrocephalus). The latter may even represent the anterior end of the large fontanelle, which has extended abnormally far into the frontal region. It sometimes occurs that the anterior end remains open for a longer period than that portion lying directly posteriorly; therefore the anterior end may become separated as a secondary fontanelle.
268
ADOLF H SCHULTZ
This distinction of Schwalbe seems somewhat arbitrary, inasmuch as all transitions can be observed in juvenile skulls. On the basis of original observations the author is convinced that the metopic fontanelle is derived from the bregmatic fontanelle, and at some time has become separated from it. Figure 4 gives the best proof. An interfrontal suture wide at its upper part, that is, a very long arm of the great fontanelle, as shown in numbers 1, 2, 3 and 4 in figure 4 is not of rare occurrence. Among 35 skulls of infants up to a few months' old the frontal arm of the great fontanelle was found to extend six times to within 10 to 17
5. Nejgro 2m.
6. Megro 5m.
8. V/hit'e i m.
A,
Fig. 4 Normae frontales of frontal bones of juvenile skulls with a long arm of the bregmatic fontanelle, which has been constricted in the lower cases to form a metopic fontanelle.
FONTANELLA METOPICA IN AN ADULT SKULL 269
mm. of the nasion. In three other cases the great fontanelle reached within 22 mm. of the nasion. This prolonged arm of the great fontanelle is an extreme variation, and is not necessarily a result of hydrocephalus. In the skull of a year old hydrocephalic negro, the author found the great fontanelle reaching to within 16 mm. of the nasion; in contrast to the cases in figure 4, however, it was, even at its lower end, 17 mm. wide; in the middle of the frontal arc 29 nun. and at its upper end 35 mm. It is striking that the lowest portions of the frontal bones always approximate
Fig. 5 Norma verticalis of a skull of erethizon dorsatus with fontanelle bones.
each other and indeed to a height which is considered typical for the position of the metopic fontanelle, that is, to a point to which the frontal arm of the great fontanella may extend uninterrupted or constricted. As a designation for the lowest portion of such long bregmatic fontanelles extending into the nasal third of the frontal arc, the name fontanella metopica may well be retained. However, no fundamental difference is to be made between the two mentioned fontanelles. It is more frequent for the lower end alone to remain patent in children and
THE AMERICAN JODRNAL OP ANATOMY, VOL 23, XO. 2
270 ADOLF H. SCHULTZ
to be recognizable in adults. The constriction of different portions of the frontal arm of the great fontanelle results from locally decreased or increased growth of the lines of ossification, and may occur in any situation, but appears to be most common between the two tubera frontalia. Double constriction to form secondary fontanelles has also been described (Rauber '06). This identity of the metopic and the great fontanelle is also demonstrated by the position of the fontanelle bones, which occur anywhere from the bregma to the upper portion of the nasal third of the frontal arc (Hartmann 1869, Barclay-Smith '09 and '10, GulUver 1890). Whether the above described case of partial persistence of the metopic fontanelle in an adult was associated with a fontanelle bone can not be determined with certainty, but seems probable, especially upon examining the inner surface.
Before any definite statements can be made as to the cause of the occurrence and partial persistence of a long frontal arm of the great fontanelle, more material must be available, and attention must be paid to correlations, especially in the frontal region. The author hopes by this contribution to stimulate interest in this anomaly in order that further cases may be reported. Observations on the occurrence of fontanelle structures in the frontal bones of mammals have been reported in a limited number, and further cases would be of great value. Among 10 skulls of erethizon dorsatus, which the author collected recently, 3 cases presented paired symmetrical fontanelle bones extending far between the frontalia. Figure 5 shows one of these cases.
FONTANELLA METOPICA IN AN ADULT SKULL 271
BIBLIOGRAPHY
Barclay-Smith, E. 1909 A rare condition of Wormian ossifications. Jour.
of Anat. and Phys., vol. 4.3, p. 277.
1910 Two cases of Wormian bones in the bregmatic fontanelle. Jour.
of Anat. and Phys., vol. 44, p. 312. Bolk, L. 1911 DieHerkunft der FontaneUametopicabeimMenschen. Anatom.
Anzeiger, Bd. 38, Ergzh., p. 195. Davida, E. 1914 Beitrage zur Persistenz der transitorischen Nijhte. Anatom.
Anzeiger, Bd. 46, p. 399. Fischer, E. 1902 Zur Kenntnis der Fontanella metopica und ihrer Bildungen.
Zeitschr. f. Morphol. und Anthrop., Bd. 4, p. 17. Gerdy, J. V. 1837 Recherches et propositions d'anatomie, depathologie et de
tocologie, etc. These de Paris, 1837, p. 5. Gulliver, G. 1890 A skull with Wormian bones in the frontal suture. Jour.
of Anat. and Phys., vol. 25. Proceedings of the Anatomical Society
of Great Britain and Ireland, Nov. 1890. Hamy, E. 1872 Ricerche suUe fontanelle anomale del cranio umano. Archivio
per I'antropol. e la etnologia II, p. 6. Hartmann, G. 1869 Beitrage zur Osteologie der Neugeborenen. Diss. Tubingen. Herpin, 1907 Evolution de I'os maxillaire inferieur. These pour le doctorat de
medccine. Paris. Maggi, L. 1894 Preinterparietale e fontanella interparietale in un idrocefalo
di Bos taurus juv. Rendiconti del Real Istituto Lombardo., vol. 27,
p. 160.
1898 Omologie craniali fra Ittiosauri e feti dell'uomo e d'altri mammiferi. Rendiconti del Real Istituto Lombardo, vol. 31, p. 631.
1899 Ossicini metopici negli uccelli e nei mammiferi. Rendiconti del Real Istituto Lombardo, vol. 32.
1899 Fontanelle metopique et frontaux moyens quadruples chez les
vertebres superieurs. Archives ital. de biologie. T. 32, fasc. 3, p. 453. Rauber, a. 1903 Zur Kenntnis des Os interfrontale und supranasale. Anatom Anzeiger. 22. Bd. p. 214.
1906 Fonticuli interfrontales inferior et superior. Gegenbaur's IMorpholog. Jahrbuch, Bd. 35, p. 354. RiccARDi, P. 1878 Studii intorno Di crani Papuani. Archivio per I'antrop.
e la etnoL, 8, p. 25. ScHULTZ, A. H. 1916 Der Canalis cranio-pharyngeus persistens beim Mensch
und bei den Affen. Gegenbaur's morpholog. Jahrbuch, Bd. L, Heft 2. ScHWALBE, G. 1899 Studien iiber Pithecanthropus erectus Dubois. Zeitschr.
f. Morphol. u. Anthrop., Bd. 1, p. 16.
1901 Ueber die Fontanella metopica (medio-frontalis) und ihre
Bildungen. Zeitschr. f. Morphol. u. Anthrop., Bd. 3, p. 93. Staderini, R. 1896 Osservazioni anatomiche. II. Intorno alia fontanella
medio-frontale del cranio umano. Alti della R. Accad. del fisiocritici.
Siena. Zanotti, 1901 La fontanella metopica ed il suo significato. Bollettino Science
Mediche, Bologna, 8, Ser. V. 2.
THE ISOLATION, SHAPE, SIZE, AND NUMBER OF THE LOBULES OF THE PIG'S LIVER
FRANKLIN PARADISE JOHNSON
University of Missouri
TWELVE FIGURES (TWO PLATES)
INTRODUCTION
The following description of the lobules of the pig's liver is based on a study of lobules that were isolated from one another by means of an acid macerating fluid. This method of isolation is invaluable in giving one a correct idea of the shape and size of the hepatic lobule, and in addition, affords a good means of approximately estimating the total number of lobules in the liver. If the maceration is stopped at just the right point, the method permits the easy dissection of blocks of liver tissue. Dissections of injected livers made in this manner, with the blood vessels and bile ducts as little disturbed as possible, give one a clearer understanding of liver structure than can be obtained by any other method.
A survey of the literature shows that to Wepfer belongs the credit of discovery of the lobule of the liver. In a letter to Paulli (1665) signed by Wepfer, 1664, the substance of the liver was described as follows:
Examine carefully boiled pig's liver; remove the external membrane and you will find the whole large mass a combination, as it were, of innumerable small glands. Concerning the livers of other animals, I confess, I have not yet made investigations. But upon thoroughly boiling a piece of pig's liver, I have seen small glands, quadrangular and other forms.
In 1666, Malpighi, unaware of Wepfer's discovery, described the lobular nature of the liver in molluscs, the lizard, ferret, mouse, squirrel, ox and man. Concerning those of man, he states:
27.S
274 . FRANKLIN PARADISE JOHNSON
Finally, in the human body if one will take the care to wash out the blood which is found in the liver by the injection of water, one will observe all the substance of the liver tissue to be composed of a number of small lobes, which resemble, as in other animals, a bunch of grapes.
The lobules were again described by Malpighi in 1683 and in his Opera Posthuma (1698), he accredited Wepfer with the priority of discovery.
A most noteworthy and often cited contribution to the subject of liver lobules is that of Kiernan, 1833. He states:
The form of the liver lobules will be now easily understood: their dimensions are known to all anatomists. They are small bodies arranged in close contact around the sub-lobular-hepatic veins, each^resenting two surfaces. One surface of every lobule, which may be called its base, rests upon a sublobular vein, to which it is connected by an intralobular vein runniriig through its center, the base of the lobule thus entering into the formation of a canal in which the sublobular vein is contained. The canal containing the hepatic veins may be called the hepatic-venous canals or surfaces ; and as the base of a lobule rests on the sublobular vein, it is evident that the canals containing these veins are fo'rmed by the bases of all the lobules of the liver. The external or capsular surface of every lobule is covered by an expansion of Glisson's capsule, by which it is connected to and separated from the contiguous lobules, and in which the branches of the hepatic duct, portal vein and hepatic artery ramify. All the lobules resemble each other in their general form, and they are all df nearly equal dimensions, they appear larger when the section is made in the direction of the hepatic vein, and smaller when in the transverse directid'n.
Although in few details the above description is incorrect, on the whole it gives one a clear idea of the arrangement of liver lobules. Kiernan's whole paper is full of splendid observations, and one may truthfully say, serves as the basis of our present knowledge of the liver. His figures illustrating the liver lobules, very probably taken from the liver of the pig, have found their w^ay into numerous textbooks of anatomy.
In 1842, Weber called attention to the fact that the lobules of the human liver are not separated from one another as in the pig, and that while lobules are indicated, the parenchyma forms a continuous mass throughout.
The work of Theile, 1884, (cited from Mall, '06) in which are described 'pseudo lobules,' gave rise to a new^ conception of the
LOBULES OF PIG's LIVER 275
structural arrangement of the liver, although Kiernan in 1833 made the statement that "the essential part of the gland is undoubtedly its duct; vessels it possesses in common with every other organ; and it may be thought that in the above description too much importance is attached to the hepatic veins." We owe to Sabourin ('82, '88) however, the discovery of the true significance of this newly recognized unit of the liver, the unit which is built around the portal canal. This unit, with its imaginary boundaries, has been discussed in recent years by Berdal ('94), Mall COO and '06) and Lewis ('04), and has been variously named the biliary lobule, portal lobule, secreting lobule and structural unit by different writers. The value of this latter concept of liver structure is no longer questioned; considered from physiological or morphological view points it stands out as the true unit of the hver. The connective tissue septa dividing the liver into hepatic lobules must be considered secondary both in point of development and importance. Yet in most animals it is the hepatic lobule which appears to be the more definite anatomical structure, and its study is essential to a clear understanding of the portal lobule. With this in mind, and without any intent to emphasize the morphological value of the hepatic lobule, the present study has been made.
THE ISOLATION OF LIVER LOBULES
The method of isolation which I first employed (Johnson, '17), that is, macerating small blocks of formalin fixed liver in 20 per cent nitric acid, I find less satisfactory than the hydrochloric acid macerating fluid used by Hiiber ('11) in the isolation of kidney tubules. The best method which I have evolved from a number of trials is as follows: Blocks of liver tissue, 1 cm. in thickness, are thoroughly hardened in 10 per cent formalin. They are then placed in 50 to 75 per cent hydrochloric acid and left standing in it at room temperature over night. Next they are placed in an oven (still in the acid) at a temperature of 50° to 60°C. In about two to four hours, depending upon the strength of the acid and the temperature of the oven, the lobules begin to fall apart. The maceration should be stopped when
276 FRANKLIN PARADISE JOHNSON
the lobules separate by gentle shaking. Care should be taken not to allow the maceration to proceed too far, yet it should not be stopped before all the connective tissue is destroyed. The blocks can be tested from time to time by gently pressing them with a dissecting needle. When the maceration is complete, the acid should be diluted four or five times with cold water and the lobules studied in this solution. (When placed in either water or alcohol the lobules disintegrate inside of a day or two.) If dissections of the liver lobules and vessels are desired, such as are shown in figures 11 and 12, maceration should be stopped when the lobules can be torn apart easily with dissecting needles. I have been unable to obtain good results in the isolation of lobules following hardening in either Zenker's or Bouin's fluid or in alcohol, and have been entirely unsuccessful in macerating fresh unfixed liver.
THE SHAPE OF THE LIVER LOBULES
The form of liver lobules is so variable that it is impossible to describe them in terms of any familiar solid. In general, it may be said that they are irregular polyhedrons of a varying number of sides, borders and angles. The surfaces may be plane, convex or concave, and may vary from as few as four or five in some of the smaller lobules to fifteen or more in some of the larger ones. The borders may be either sharply marked or rounded, while the angles formed by the union of the borders may vary from sharply acute to greatly obtuse.
So far as shape alone is concerned I have found no way of determining on which surface the hepatic vein leaves the lobule, the surface which Kiernan ('33) describes as the base. Its point of exit may be either a small or large surface, plane, convex or concave, or it may even proceed from one of the borders or angles of the lobule (figs. 5, 6, 9 and 10).
The surface lobules (figs. 1, 5, 9 and 11) are in many instances distinguishable from the deeper lobules in that they are often irregularly prismatic in shape, their external surfaces are usually slightly convex and the shape of a four, five or six-sided polygon ; the sides are plane or only slightly curving and more or less rec
LOBULES OF PIG's LIVER 277
tangular. The deeper ends of these lobules are usually irregular in shape and quite often larger or smaller than the surface ends. Occasionally are to be seen lobules which are markedly pyramidal in shape, the apices of which may be directed either toward or away from the surface of the liver.
The fact that the lobules of the liver are closely packed solids leads to the question whether or not they resemble any of the regular geometrical solids which fill space. Of such solids, in addition to three, four and six-sided prisms, may be mentioned the tetrahedron, hexahedron, dodekahedron and the tetrakaidekahedron. The surface lobules, as stated above, tend to be prismatic, but I have found but few of the deeper lobules which approach in form any of the above named geometrical solids. Occasionally, however, one may be found which meets the requirements of one of these solids when viewed from one side, but fails when viewed from the other. Several such lobules are shown in figures 1, 2 and 6. If there is any attempt in development to cut the liver up in similarly shaped units, the adult condition does not show it. It should be further pointed out that the lobules in young stages of the pig, amongst them stag-es in which the lobules are just beginning to be marked off from one another, likewise show but very few regularly-shaped lobules. Among the factors which might tend to break up any uniformity in the shape of the lobules may be mentioned the' splitting up of the lobules to form additional ones (Johnson, '17) the unequal growth and size of the variou3 lobules, and the presence of the portal and hepatic canals.
The statement that the lobules of the pig's liver are completely separated from one another by connective tissue septa is prevalent in anatomical literature. While this is true of the majority of lobules, it will not hold for a large number of them. If a block of liver tissue is macerated in hydrochloric acid there will be seen amongst the completely separated lobules a number which cling together in small clumps of from 2 to 6 lobules each, figures 7, 8 and 10. The individual lobules of these clumps cannot be isolated by shaking or gentle teasing, and a definite tearing of the liver parenchjmia is necessary in order to divide them.
278 FRANKLIN PARADISE JOHNSON
The clumps, therefore, must be considered as compound lobules" (Kiernan) and are due to incomplete connective tissue septa. They undoubtedly are the result of the failure of the septa to grow completely across the lobules in the developing liver, at the time when the lobules are dividing to form additional ones. The evidence of incomplete septa can often be seen in ordinary sections of the adult pig's liver.
THE SIZE AND NUMBER OF THE LIVER LOBULES * .
The size of the lobule of the adult pig's liver is very variable, great differences existing within any individual liver. The smallest lobules may be no larger than 0.5 mm. in diameter; the largest ones may be 2 mm. or over. Assuming that the shapes of the large and small lobules are approximately similar, it is evident that the largest lobules must be as much as 64 times greater by volume than the smallest ones.
The average volume of the liver lobule is dependent to a certain degree upon the size of the liver, thus in small livers the average volume is less than in large ones. This is shown in the accompanying table.
The total number of lobules in the pig's liver is also quite variable. This can be readily observed with the naked eye when examining isolated lobules of different livers of approximately the same weight — in some the majority of lobules are large while in others they are decidedly smaller.
The method of calculating the average size and number of hepatic lobules, which I have found most satisfactory, is as follows : Rectangular blocks of formalin-fixed liver, with dimensions between 1 and 2 cm., were taken from a liver of known weight. ■Each block was carefully weighed, placed in a separate dish in 50 per cent hydrochloric acid over night, and then in an oven at a temperature of from 50° to 60 °C. After about an hour the surface lobules become swollen and each projects slightly from the surface. The surface lobules now being definitely marked off from one another, were counted under a hand-lens, care being taken not to count twice those lobules on the borders and corners of the block. The block was again placed in the oven and
LOBULES OP PIG S LIVER
279
maceraton allowed to proceed until the lobules separated. The lobules were then counted under a hand-lens, a few- being taken out at a time with a pipette and removed to a watch glass. In counting, the individual parts of compound lobules were con-' sidered as separate lobules; so also were the cut portions of the lobules which came from the cut surfaces of the block. This number was reduced by one-half the number of surface lobules counted, since I assumed that in slicing a piece of liver, the sum of the cut lobules on one side equals the sum of those on the other. Dividing the number of lobules obtained in this way into the weight of the block gives the weight per lobule, and the weight per lobule into the weight of the liver gives the total number of lobules. The average of a number of counts on nine different livers are given in the table below. The average weight per lobule obtained is 2.41 milligrams and the average number of lobules 702,000. The latter number is somewhat higher than that (480,000) obtained by Mall as the average number of lobules in the dog's liver.
TABLE 1
WEIGHT OF LIVER
AVERAGE WEIGHT PER LOBULEI
NUMBER OF LOBULES
grams
mgm.
1.132
1.95
570,000
1203
1.40
859,000
1418
2.02
541,000
1658
1.95
850,000
1658
2.21
750,000
1786
2.36
757,000
1886
3.99
472,000
1927
2.98
647,000
1942
2.22
874,000
Average. _
2.41
702,000
' The "average weight per lobule" was obtained fro.ii calculations based on counts from several blocks taken from each liver.
280 FRANKLIN PARADISE JOHNSON
BIBLIOGRAPHY
Berdal 1894 Elements d'histologie normale, Paris.
HuBER, G. Carl 1911 A method for isolating the renal tubules of mammalia.
Anat. Rec, vol. 5, pp. 187-194. Johnson, Franklin P. 1917 The later development of the lobule of the pig's
liver. Anat. Rec, vol. 11, pp. 371-372. KiERNAN, Francis 1833 The anatomy and phj'siologj^ of the liver. Phil.
Trans. London, pp. 711-770. Lewis, F. T. 1904 The question of sinusoids. Anat. Anz., Bd. 25, pp. 261-279. Mall, Franklin P. 1900 The architecture and blood vessels of the dog's
spleen. Zeit. f. Morph., vol. 5. Anthropol. pp. 1-42.
1906 A study of the structural unit of the liver. Am. Jour. Anat.,
vol. 5, .pp. 227-308. ^
Malpighi, Marcello 1666 De viscerum struotura exercitatio anatomica.
Bononiae.
1683 Exercitationes de structura viscenmi. Francofurti.
1698 Opera Posthuma, Amstelodami. Paulli, Jac. Hen. 1665 Anatomiae Bilsianae Anatome — accessit excellentis simi viri D. Jo. Jac. Wfepferi de dubiis Anatomicis Epistola, cum
Responsione. Argentorati. p. 97. Sabourin, Ch. 1882 Considerations sur I'anatomie typographique de la gland
biliaire de I'homme. Revue de medecine, Paris, vol. 2, pp. 40-57.
1888 Recherches sur I'anatomie normale et pathologique de la glande
biliaire de I'homme. Paris. Weber, E. H. 1842 Annotationes anatomicae et physiologicae, Prol. VIII
Weinlig, R. C. and Buddeus, A. Leipzig.
PLATE 1
explanation of figures
Isolated liver lobules drawn at a magnification of 12.5 diameters. The greatest extremes in sizes are not shown. 1, 5, 9 Surface lobules 1, 2, 6 Geometrical forms. 7, 8, 10 Compound lobules.
LOBULES OF PIG'S LIVER
FRANKLIN PARADISE JOHNSON
PLATE 1
281
PLATE 2
EXPLANATIO>f OF FIGURES
Dissections of liver lobules to show their arrangement.
11 A group of sui-face lobules. Bile ducts and branches of the hepatic arteryhave been omitted.
12 A group of lobules situated deep in the substance of the liver. On the left is seen a large portal canal with bile duct, hepatic artery, and portal vein. The branches of these vessels were worked out as far as possible. Undoubtedly some of them were torn away in lifting off the lobules in dissecting, so that all the branches ramifying over the surfaces of the lobules are not shown, p.v., portal vein; s.v., sublobular (hepatic) vein; c.v., central (hepatic) vein; b.d., bile duct; h.a., hepatic artery.
282
LOBULES OF PIG'S LIVER
FEANKHN PARADISE JOHNSON
PLATE 2
283
AnXHOR'S ABSTRACT OF THIS PAPER ISSUED BY THE BIBLIOGRAPHIC SERVICE FEBRUARY 2
THE BRACHIAL PLEXUS OF NERVES IN MAN, THE
VARIATIONS IN ITS FORMATION AND
BRANCHES
ABRAM T. KERR
From the Department of Anatomy, Cornell University Medical College, Ithaca, N. Y.
TWENTY-NINE FIGURES
INTRODUCTION AND METHODS
This paper is based upon records of dissections from the Anatomical Laboratory of the Johns Hopkins Medical School during the years 1895 to 1900, and from the Anatomical Laboratory of the Cornell University Medical College, Ithaca, at intervals from 1900 to 1910.
The dissections were made in most cases by the regular medical students who, after uncovering the peripheral nerves with much care, made records and diagrams of the course, relations, and connections of these nerves.
The dissections were carefully supervised by the instructors as well as by the persons in charge of this investigation. These latter always compared minutely the drawings with the dissection, corrected errors, and wherever necessary made more complete dissections and worked out the finer details. They also recorded the character and accuracy of the dissection and drawing.
The diagrams were compared with the dissections and verified by Dr. A. W. Elting from 1895 to 1897 and by Dr. C. R. Bardeen from 1897 to 1899. The Johns Hopkins records in 1899 to 1900 as well as all the Cornell records were verified by the writer.
From 1895 to 1899, the Elting printed tabular Hsts of the names of the nerves were used. These were so arranged that the relations and connections of the nerves could be indicated
285
THE AMERICAN JOURNAL OF ANATOMY, VOL. 23, NO. 2
286 ABRAM T. KERR
by underlining, erasing, or inserting the names n the proper place. They were in many cases accompanied by free hand sketches of the arrangement of the nerves and only those records that were accompanied by satisfactory diagrams have been used in this paper. Beginning in 1899, the records were made on the Bardeen Outline Record Charts (Bardeen '00) as prepared under Dr. Bardeen's direction by the writer for the upper extremity. At first the outline record charts were used at Cornell but later the students made natural size drawings.
Between four and five hundred records were preserved. From these I have selected only those diagrams about the accuracy and scientific value of which I could feel no doubt. These number 175. Records have been rejected for various reasons. In some cases, the condition of the dissecting material made it impossible to obtain satisfactory dissections. Lack of manual dexterity or careless dissection made the work of some students of no value. In other cases, the inability of the student to draw accurate or clear diagrams made their records worthless. A considerable number of records which were otherwise accurate were excluded because they did not record the relation of the fourth cervical nerve to the plexus.
It not infrequently happened that the record of the plexus as a whole was satisfactory but the record of one or more of the branches had to be discarded, either because the branch was broken or because, at the time the record was verified, its distribution had not been sufficiently worked out. The record of such a plexus has often been included in this series but has not been used for the study of the doubtful branch or branches. For this reason the number of the records of different branches varies considerably.
Although age would seem to have very little influence upon the course and distribution of the nerves, nevertheless the ages of the cadavers were considered. They were obtained in most cases from the records. In the' remainder, they were estimated as accurately as possible. They ranged from infancy to senility.
The color of the subjects used was determined in most cases from the records. Without the records it was often difficult to
BRACHIAL PLEXUS OF NERVES IN MAN 287
distinguish, in the embalmed bodies, light mulattoes from dark whites, and in any case, it -was quite impossible to tell whether the colored subjects were pure bloods or were a mixture of negro and white. It is probable that in a great proportion of the cases they were not full blooded negroes. It must be remembered also that the so-called American negroes came from tribes or races of African negroes. In the white bodies, likewise, undoubtedly several and mixed nationalities were represented.
In this paper the number of plexuses and not the number of bodies is given, since not infrequently the dissection or record of one side of the body only was complete or suitable for scientific purposes. In the cases where satisfactory records of both sides were obtained the question of symmetry and asymmetry has been considered in a separate section.
A preliminary statement of the results of the part of this investigation dealing with the formation of the brachial plexus was presented at the 21st session of the American Association of Anatomists in December, 1906, and a synopsis of the findings was published in the American Journal of Anatomy (Kerr '07). A preliminary account of the findings in regard to the subscapular group of nerves was presented at the 23rd session of the American Association of Anatomists in January, 1908, but no record of these statistics has been published.
Much credit for the success of the undertaking is due not only to the students for their careful dissections and records but also to the instructors in charge of the dissection for their interest and cooperation.
I undertook this work at the suggestion of Dr. F. P. Mall, to whom I am greatly indebted for many valuable suggestions. To Dr. C. R. Bardeen I am likewise indebted for much advice and help. I also wish to express my appreciation for the many courtesies extended by Dr. R. G. Harrison. My thanks are due to Drs. Bardeen and Elting for permission to use the records verified by them.
288 ABRAM T. KERR
DISTRIBUTION OF THE MATERIAL USED AS TO SEX, COLOR AND
SIDE OF THE BODY
It has been possible to divide the plexuses into certain groups and an attempt has been made to determine if one variety of plexus occurs more frequently in white or in colored subjects, in the male or in the female sex, and upon the right or the left side of the body. As the 175 plexuses which were found satisfactory were selected wholly with regard to the accuracy of the record it is at once clear that there would not be an equal number of male and female, white and colored, right and left plexuses. In order to be able to determine the percentage of frequency of each type of plexus among the sexes, the colors, and the sides of the body, it is necessary first to classify the material used.
Table V shows how irregular this distribution is. It will be seen that 1 14 of the 175 plexuses or 65.14 per cent are from males, while there are only 61 or 34.85 per cent from females. That is, there are only slightly more than half as many from females as from males.
Of the 114 plexuses from males, 65 are from white and 49 from colored subjects and of the 61 plexuses from females, 20 are from white and 41 from colored subjects. That is, the number from white males is slightly greater than the number from colored males, while there are more than twice as many plexuses from colored as from w^hite females. In spite of this, because of the large proportion of white males, the total number of plexuses from colored subjects (90) is only slightly more than the total number from white subjects (85).
Taking each sex separately or both combined, the plexuses will be seen to be distributed nearly equally on the two sides of the body. This is quite independent of the total number of bodies, since, as already noted, the records from both sides of all of the bodies are not included in the series.
SPINAL NERVES FORMING THE BRACHIAL PLEXUS
All anatomists are agreed that, in man, the anterior rami (ventral primary divisions) of the caudal four cervical nerves
1 For tables see pp. 376-380.
BRACHIAL PLEXUS OF NERVES IN MAN 289
and a part of the first thoracic nerve^ always enter into the formation of the brachial plexus. There is more or less vagueness, however, as to the frequency with which one or both of the nerves adjoining these nerves cephalad and caudad also send branches to the plexus. Thus different authors state that there is 'sometimes' a fasciculus from the fourth cervical to join the plexus or that 'frequently,' or 'in many cases' or 'usually' such a branch is present, and similarly that a filament from the second thoracic nerve is found, 'sometimes,' 'frequently,' 'usually,' 'in many cases,' or 'not rarely.' In other words, all are agreed that the anterior rami of at least five spinal nerves enter into the formation of the plexus in all cases, but they are not at all clear as to how frequently there may be six or possibly seven nerves entering the plexus.
In this report, the cephalic limits of the plexus are noted in all instances. The records of the caudal limits are, however, not included, as it was possible to obtain satisfactory records in so few cases that it was thought best to exclude these entirely from •the main statistical tables. In some cases the records of the caudal limits of the plexus were not obtained because the second thoracic nerve can only be exposed when the thorax is opened and in many instances this was dissected by a different student than the dissector of the upper extremity. In other cases the nerves were surrounded by strong parietal pleuritic adhesions or were embedded in the shellac mass used for injecting the blood vessels so that it was not possible to make a satisfactory dissection.
Eckhard ('62), Kaufmann ('64), Cunningham ('77), Adolphi ('98) and others have shown that the second thoracic nerve, at times contributes to the brachial plexus. Cunningham found the second thoracic nerve joining the first in 27 out of 37 cases. He says, "Sometimes the connecting twig was very large, sometimes very fine and seen with difficulty. It may be single, double or triple. When double, usually one twig joins the intercostal
2 For the sake of brevity, the terms fourth cervical nerve, fifth cervical nerve, etc., will be used in most cases instead of anterior ramus of the fourth cervical nerve, etc.
290 ABRAM T. KERR
and one the brachial branch of the first thoracic nerve." Harman ('00) found the connection in 7 out of 12 dissections. Paterson ('96) found the connection in only 11 out of 33 cases. Harris ('04) states that it is "only in the postfixed types, in which it might be expected" that the second thoracic nerve joins the first and thus contributes to the plexus. Cunningham (77) believed that the branch from the second thoracic nerve to join the brachial plexus is influenced by the size of the intercostobrachial nerve. Adolphi ('98) thinks that there is no reciprocal relation between the second thoracic branch to the first and the intercostobrachial nerve. He considers this connection a variation that is associated with a more cephalic or caudal type of plexus and with variations of the thorax and vertebral column. Birmingham ('95) has shown how the communication between the first and second thoracic nerves contributes to the intercostal nerves. The intimate relation and the variability of the connection between the first and second thoracic nerves and the neighboring sympathetic ganglia has been pointed out by Harman ('00).
From the above statement it is clear, I think, that there is much difference of opinion among anatomists concerning the arrangement and connections of the nerves of this region and that they are not well understood and need further study.
DIVISION OF THE PLEXUSES INTO GROUPS
In studying the plexuses it was seen at once that they varied in the number and amount of cervical spinal nerves entering them at their cephalic border.
All those plexuses in which a branch from the fourth cervical nerve enters the plexus fall into one group that has been designated as group 1. The size of this branch varies from a minute twig to a branch as large as the average suprascapular nerve. The group has not been subdivided because of the difference in size of the branch from the fourth nerve. There are 110 of the 175 satisfactory records or 62.85 per cent of the cases that fall in group 1.
BRACHIAL PLEXUS OF NERVES IN MAN 291
There is another group of plexuses in which the whole of the fifth cervical nerve enters the plexus without any additions from the fourth cervical. This type has been called group 2. There are 52 records or 29.71 per cent of the cases in group 2.
There is a third group of plexuses, to be known as group 3, in which not only does no part of the fourth cervical nerve enter the plexus but also the plexus does not receive the whole of the fifth cervical nerve. A portion of the fifth cervical joins with the fourth to aid in the formation of the cervical plexus. There are 13 plexuses or 7.42 per cent of the cases in group 3.
In round numbers we find then that in over 62 per cent of the cases the fourth cervical nerve sends a branch to the brachial plexus and in about 37 per cent it does not. That in this latter case the whole of the fifth cervical nerve enters the plexus in nearly 30 per cent of the cases and only part of the fifth cervical contributes in over 7 per cent.
The three groups into which the plexuses have been divided may be briefly described as follows:
Group 1, in which a part of the fourth cervical nerve enters the plexus, and containing 62.85 per cent of the plexuses (fig. P) ;
Group 2, in which the fourth cervical nerve does not enter the plexus but the whole of the fifth cervical nerve does, and containing 29.71 per cent of the plexuses (fig. 2);
Group 3, in which onl}^ a part of the fifth cervical nerve joins the plexus, and consisting of only 7.42 per cent of the cases
(fig. 3).
Group one
From table 2, it will be observed that 70 of the 110 plexuses in group 1 are from males and 40 of them from females, or 63.63 per cent of the group are from males and 36.36 per cent are from females. There are, however, only 61 plexuses from females while there are 114 from males, table 1. Forty of the 61 plexuses from females are found in group 1, or 65.57 per cent of the female plexuses, table 6. Seventy of the 114 plexuses from males are found in this group, or 61.40 per cent of the male
3 For figures see pp. 381-395.
292 ABRAM T. KERR
plexuses, table 5. We thus see that comparing each sex separately there are over 4 per cent more plexuses from females than from males belonging to group 1.
There are 41 plexuses from white males among the 110 plexuses in group 1 or 37.37 per cent of the group, and 29 plexuses from colored males or 26.36 per cent of the group. There are in all 65 plexuses from white males, and 41 of these or 63.07 per cent are in group 1. Of the 49 plexuses from colored males, 29 or 59.18 per cent are in group 1. It would appear then that among males, the brachial plexus receives a branch from the fourth cervical nerve 3.89 per cent more frequently among the white than among the colored.
Thirty-four of the 110 plexuses in group 1 are from the right side of male subjects, or 30.90 per cent of the group, 36 or 32.72 per cent are from the left side of male subjects, a difference of less than 2 per cent, table 2. Of the 56 right male plexuses studied, 34 or 60.71 per cent are in group 1 and of the 58 left male plexuses studied, 36 or 62.06 per cent are in this group, a difference in favor of the left of 1.35 per cent.
Fifteen, or 13.63 per cent of the 110 plexuses in group 1 are from white females, and 25 or 22.72 per cent of the group are from colored females. There are in all 20 plexuses from white females, and 15 of these, or 75 per cent are in group 1. Twentyfive, or 60.97 per cent of the 41 plexuses from colored females are in gi^oup 1. Group 1 plexuses would appear to occur over 14 per cent more often among white than among colored females.
There are 20 right and 20 left plexuses from females that fall in group 1, 18.18 p^r cent of the group in each case. Of the 31 female plexuses from the right side, 20 or 64.51 per cent are in group 1, and of the 30 female plexuses from the left side, 20 or 66.66 per cent are in the group, a difference in favor of the left of 2.15 per cent.
As regards the two sides of the body, the plexuses in group 1 are distributed nearly equally, 54 on the right side and 56 on the left side, table 2. The total number of plexuses considered is distributed nearly equally between the two sides of the body, 87 on the right side and 88 on the left side. It will be seen then that
BEACHIAL PLEXUS OF NERVES IN MAN 293
62.06 per cent of the plexuses from the right side of the body are in group 1, table 9, and 63.63 per cent of the left plexuses are in this group, table 10, a difference of but 1.57 P^i" cent in favor of the left side.
Of the 110 plexuses in this group, 56 are from white and 54 from colored subjects, or 50.90 and 49.09 per cent of the group respectively, a nearly equal distribution, table 2. But 65.88 per cent of the 85 plexuses from white bodies, and 59.99 per cent of the 90 plexuses from colored bodies are found in group 1 . That is, 5.89 per cent more of the plexuses from white than of the plexuses from colored bodies fall in this group.
Forty-one of the 65 white male plexuses or 63.07 per cent of them are in group 1, and 15 of the 20 white female plexuses or 75 per cent of them are in this group, a difference of 11.93 per cent in favor of the white female.
Twent^^-nine of the 49 plexuses from colored males are in group 1, or 59.18 per cent, and 25 of the 41 plexuses from colored females are in this group, or 60.97 of them. This gives a difference in favor of the colored females of but 1.79 per cent.
Group two.
From table 3, which shows the distribution of the plexuses from group 2, it will be seen that of the 52 plexuses in the group, 35 are from male and 17 from female bodies, that is, 67.30 per cent from males and 32.69 per cent from females, or more than two to one. Of the total of 114 plexuses from males, 35 fall in group 2 or 30.70 per cent, and of the 61 from females, 17 are in group 2, or 27.86 per cent which shows less than 3 per cent of difference in favor of the males.
Of the 52 plexuses in group 2, 18 are from white males and 17 are from colored males, or 34.61 per cent from whites and 32.69 from colored, table 2. There is a total of 65 plexuses from white males and 18 of them or 27.69 per cent are in group 2. Of the 49 plexuses from colored males, 17 are in this group or 34.69 per cent a difference in favor of the colored males of 7 per cent.
Nineteen of the 52 plexuses in group 2 are from the right side of males and 16 from the left side, or 36.53 per cent right and
294 ABRAM T. KERR
30.77 per cent left, a difference in favor of the right of 5.76 per cent, table 6. Of the 56 plexuses from the right side that \Aere studied, 19 are in group 2, or 33.92 per cent, and of the 58 plexuses from the left side, 16 or 27.58 per cent are in this group. This gives a difference of 6.34 per cent in favor of the right side.
There are but 3 plexuses from white females in group 2, as against 14 from colored females. This gives a difference in percentage occurrence of over 21, table 2. Of the 20 plexuses from white females studies, 3 are in group 2, or 15 per cent, while 14 of the 41 plexuses from colored females are in this group, or 34.41 per cent. . This gives a difference in favor of the colored of 19.14 per cent.
Nine of the 52 plexuses of group 2 are from the right side of female subjects and 8 from the left side, or 17.30 per cent and 15.38 per cent of the group respectively. Of the 31 plexuses from the right side of female bodies that were studied, 9 or 29.03 per cent are in group 2 and of the 30 from the left side, 8 are in this group, or 26.66 per cent, a difference in favor of the right of 2.37 per cent.
Upon the right side there are 28 plexuses in group 2, that is, 53.84 per cent of the group, and upon the left side there are 24, or 46.15 per cent. There are 28 right plexuses in group 2 out of a total of 87 rights or 32.18 per cent, and out of a total of 88 left plexuses 24 fall into group 2 or 27.27 per cent which shows that in this series, group 2 plexuses are found 4.91 per cent more often - on the right side.
About three-fifths of the plexuses in group 2 are from colored and two-fifths from white subjects. Table 3 shows that 21 or 40.38 per cent of the group are from white subjects and 31 or 59.61 per cent are from colored subjects. Twenty-one of the 85 plexuses from white bodies or 24.70 per cent, and 31 out of 90 from colored bodies or 34.44 per cent are in group 2. It would appear then that this group of plexuses is 9.74 per cent more common in colored than in white subjects.
The 21 plexuses from white subjects are 18 from males and 3 from females. Comparing this with the total number from white males, 65, and from white females, 20, we have 27.69 per cent
BRACHIAL PLEXUS OF NERVES IN MAN 295
among the white males and 15 per cent among the white females occurring in group 2, a difference of 12.69 per cent in favor of the white males.
The 31 plexuses of group 2 from colored subjects are 17 from males and 14 from female^. Compared with the total number of plexuses from male and female colored subjects, namely 49 and 41, we have 34.69 per cent of group 2 among the colored males and 34.14 per cent among the colored females, a nearly equal distribution between the two sexes among the colored.
From the above, it will be seen that while group 2 occurs among colored males and females about equally often, that it is found very much more often among the white males than among white females.
Group three
Table 4 shows that of the 13 plexuses in this group 9 are from male subjects or 69.23 per cent and that 4 are from females, 30.76 per cent, that is, that more than twice as many are from males as from females. Comparing the number of male and female plexuses in this group with the total number of records from each sex, tables 5 and 6, we find that among the 114 plexuses from males, 9 are in group 3 or 7.89 per cent, and among the 61 plexuses from females, 4 are in group 3 or 6.55 per cent. This shows a variation of but slightly over 1 per cent.
It will be seen from table 4 that 3 of the plexuses, 23.07 per cent, of group 3 are from colored males and 6, 46.14 per cent, are from white males, or exactly 1 to 2. Six of the 65 plexuses from white males or 9.23 per cent are in group 3, and 13 of the 49 plexuses from colored males or 6.12 per cent are in this group, a difference in favor of the white males of only 3.11 per cent.
There are twice as many plexuses in this group from males on the left as on the right side, that is, 6 to 3. Six of the 58 plexuses from the left side of male subjects or 10.34 per cent and only 3 of the 56 from the right side or 5.35 per cent are in group 3, a difference of 4.99 per cent.
In group 3 the plexuses are distributed equally between colored and white females, 2 of each, as the total number of plexuses from
296 ABRAM T. KERR
colored females is 41, the 2 in group 3 form 4.87 per cent, while the 2 from white females form 10 per cent of the total of 20 from white females that are in group 3.
Among the females of the group the plexuses are also distributed equally on the right and left sides, 2 on each. Of the 30 plexuses from the left side of the females, 2 or 6.66 per cent are in group 3 and 2 of the 31 or 6.45 per cent are from the right side, which makes the percentage nearly the same on both sides.
Five of the thirteen plexuses of group 3 are on the right and 8 on the left side, that is, 38.46 per cent on the right and 61.53 per cent on the left, a difference of 23.07 per cent in favor of the left side. Five of the 87 right plexuses that were studied or 5.74 per cent and 8 of the 88 left plexuses or 9.09 per cent are in group 3, a difference of 3.35 per cent in favor of the left.
Eight or 61.53 per cent of this group are from white and 5 or 38.46 per cent are from colored subjects. Compared with the total number of records from white and colored, 85 white and 90 colored, tables 7 and 8, we see that 9.41 per cent of the plexuses from white and 5.55 per cent of the plexuses from colored subjects are in group 3, or 3.86 percent more white than colored.
There are three times as many plexuses from white males as from white females, in this group. The 6 plexuses in this group from white males constitute 9.23 per cent of the total of 65 plexuses from white males while the two plexuses from white females form 10 per cent of the 20 plexuses from white females.
There are 3 plexuses in this group from colored male to 2 from colored female subjects. Of the total of 49 plexuses from colored males, 3 or 6.12 per cent are in group 3 while of the total of 41 from colored females, 2 or 4.87 per cent are in this group, a difference of only 1.25 per cent.
INFLUENCE OF SEX, COLOR, AND SIDE OF THE BODY UPON THE
PLEXUSES
The above comparisons of the frequency of occurrence of each group of plexuses among white and colored, male and female, and upon the right and left sides of the body have been made in
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two ways: first, within the group, that is, by comparing the number of plexuses in the group from white, colored, male and female, right or left, with the total number of plexuses in the group; secondly, by comparing the number of male plexuses in the group with the total number from males studied and the number from females in the group with the total number from females studied, etc. I consider the latter far the more accurate and shall use that almost entirely in the following comparison of the three groups.
Although comparing the plexuses of each group separately, because of the great preponderance of plexuses from males, the percentage of the plexuses from this sex greatly exceeds those from females, yet if we take the plexuses from males and females of each group and compare them with the total number of plexuses from males and from females it will be seen that groups 2 and 3 occur more often among the males and group 1 among the females. That is, that plexuses in which the fourth cervical nerve enters, plexuses which have the most cephalic origin, occur more often among females than among males. This seems to indicate that the plexus in the female tends to be more cephalic in position than in the male. But we find that the difference in the frequency of occurrence of plexuses from males over females in group 2 is 2.84 per cent but in group 3 is but 1.34 per cent; while if much of any significance were to be given to the greater frequency of group 1 among females we should expect to find them least frequent in group 3, the most caudal group, and not in group 2 intermediate, which happens to be the case.
Furthermore, if we take the plexuses from colored and white males and females of each group and compare them with the total number of colored and white males and females respectively, we find that in group 1 the percentage of colored males is 1.79 less than the percentage of colored females; in group 2, 0.55 per cent more colored males than females; and in group 3, 1.25 per cent more colored males than females. On the other hand the percentage of plexuses from white females exceeds the percentage from white males by 11.93 per cent in group 1; the percentage from white males exceeds the percentage from white
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females by 12.(59 per cent in group 2, and the percentage from white males exceeds the percentage from white females by .77 per cent in group 3. It must be remembered also that the extreme variation is but a few per cent.
Plexuses of group 2 occur more often on the right side and groups 1 and 3 on the left. Since there is a more or less gradual change from a cephalic to a caudal position in passing from group 1 to group 3 it is difficult to attach any significance to the fact that group 1 occurs 1.57 per cent more often on the left side, group 2, 4.91 per cent more often on the right, and group 3, 3.35 per cent more often on the left.
Whether the form of the plexus is influenced by or influences right and left handedness it was impossible to tell as there was no record as to whether the subjects had been -right or left handed. It is altogether improbable that so large a proportion more than half were left handed.
Plexuses of groups 1 and 3 occur more often in white and of group 2 in colored subjects. We have here the same conditions as for the two sides of the body only here the percentage of difference is greater. The difference in percentage in favor of the white is 5.89 per cent in group 1, and 3.86 per cent in group 3; while it is 9.74 per cent in favor of the colored in group 2.
I ani' quite convinced that so far as this investigation has been carried it does not sho\V that sex, color or side of the body has any influence whatever in determining the group of plexus.
It will be noted that in many of these subdivisions but a small number of cases are-considered and that the percentages of variation are in no case great. It would seem not at all improbable that if a greater number of cases were considered equally distributed among the sexes, colors, sides, etc., that the irregularity in this particular would be much less marked.
CEPHALIC AND CAUDAL POSITION OF THE PLEXUS
Various authors have classified the brachial plexus as cephalic and caudal, high and low, or prefixed and postfixed, meaning b}this a i)osition or strength of the plexus nearer to or farther from the head end of the body. The classifications are usually based
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upon the position of the plexus along the body axis. Those plexuses that receive branches from the fourth cervical nerve would be more cephalic than those that do not. The terms have been used by some, especially prefixed or postfixed, to indicate the position of the supposed greatest strength of the plexus, that is, the position of the largest nerves.
The plexuses of group 1, in which a branch from the fourth cervical nerve joins the plexus may be classified as cephalic, those of group 3 in which the fifth cervical nerve sends a branch to the cervical plexus as caudal, while those of group 2 in which the fifth neither receives nor gives off a branch as intermediate.
Between the most cephalic plexuses of group 1, with the largest sized branch from the fourth cervical nerve and the most caudal plexuses of group 3, with the largest branch from the fifth to the fourth, there is a variation of almost one spinal nerve. This may be accounted for either by a shifting of the plexus along the spinal cord in either a cephalic or a caudal direction without change in its relative size or the number of elements entering it, or by an increase or decrease in the number of nerve fibers entering the plexus.
If it is a shifting of the plexus that takes place, then when the branch of the fourth cervical nerve is large the branch from the second thoracic should be wanting, and when the fifth sends a branch to the fourth there should be a large branch from the second thoracic nerve to the plexus.
If it is an increase or decrease in the number of nerve fibers that enter the plexus that occurs, then the expansion or contraction of the plexus may take place on its cephalic or caudal side or both.
From my own observations just given it is obvious that there is a variation in the cephalic limits of the plexus but unfortunately I have been able to study the caudal limits in only a few of these plexuses. Moreover, I have been able nowhere to find records of cases which show that when the fourth cervical nerve does not enter the plexus the second thoracic invariably does, and inversel}", whether when -the fourth cervical nerve enters into the formation of the plexus the second thoracic does not, or as to
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whether there is a relation in size between these two nerves when they both enter the plexus. The few cases that I have examined seem to indicate an expansion and contraction of the plexus rather than a shifting of it along the cord. I hope that soon we may have sufficient records so as to be able to determine this more definitely. We must bear in mind that in the spinal cord there are rows or columns of cells extending its whole length from which the nerve fibers take origin or around which they end. The cells are not, so far as we know, arranged in groups corresponding to the groups of fibers in the root fila or in the nerves. The nerve fibers in the case of motor nerves extend from the cells in the gray matter of the cord towards its periphery and then break through the periphery and extend beyond the periphery in groups, the root fila. In the case of the sensory nerves they extend in the opposite direction, that is centrad. The fila radicularia are arranged in continuous rows separated from one another, as a rule, by slight intervals, which are generally somewhat greater between the fila of one nerve and those of the one next cephalad or caudad. As they pass laterad, groups of the fila converge and are joined together into the dorsal and ventral nerve roots. The segmental subdivision of the adult spinal cord in based entirely upon the points of attachment to the cord of the groups of root fila that converge to join a single pair of nerves. Whether or not the same number of nerve fibers enter the same filum in different individuals is not known but it is altogether probable that there is a variation in this respect. We do know that there is a variation in the number of fila which join to form a given ventral root and dorsal root. It is easy to understand how either the appearance of shifting of the plexus along the spinal cord or of its expansion might be produced by variation in the grouping of the fila as they converge to form the nerves, the number of nerve fibers remaining the same.
PREFIXED AND POSTFIXED PLEXUSES. RELATIVE SIZE OF THE
NERVES
As already noted some anatomists divide the brachial plexus into prefixed and postfixed groups based upon the position in the
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plexus of the strongest elements, that is, the nerves with the greatest diameters.
I have attempted in 27 cases to classify the plexuses in this way, table 11. The anterior rami of the spinal nerves entering the plexus were measured as soon as the surrounding connective tissue was removed. The measurement was made while the plexus was still connected to the spinal cord, that is, before the upper extremity was separated from the body. The diameters were taken with sharp pointed dividers and the measurements were recorded by sticking the points of the dividers into the paper, upon which the diagram of the plexus was made.
Twenty-one of the plexuses are in group 1, and receive a branch from the fourth cervical nerve. This is the smallest branch entering the plexus, it being remembered that the branch from the second thoracic is not considered.
If we disregard the fourth cervical, the smallest nerve entering the plexus is the fifth cervical in 11 instances, and fifth cervical and the first thoracic equally in 9, and the first thoracic in 7. In the 11 cases where the fifth cervical is the smallest, the first thoracic is next in size — the sixth is equally large in 3 of these, the sixth, seventh and eighth in 1 and the seventh in 1. In the 7 instances in which the first thoracic is the smallest nerve, the fifth cervical is the next in size in 5, in two of which the eighth is equally small. The sixth cervical is the nerve of second size in 1 and the eighth in 1 .
In the 27 cases, the nerves with the greatest diameter entering the plexus are the seventh cervical nerve in 7 cases, 5 in group 1, 2 in group 3; the eighth cervical nerve in 6 cases, 5 in group 1, 1 in group 3; and the sixth cervical nerve in 2, 1 each in groups 1 and 2. The seventh and eighth cervical nerves are equal in diameter and are the largest nerves in 6 cases, 5 in group 1 and 1 in group 2; the sixth, seventh and eighth cervical are equal and largest in 2 cases both in group 1 ; the first thoracic, sixth, seventh and eighth cervical nerves are equal and the largest in one instance in group 3; the sixth and seventh cervical nerves are equal and are the largest nerves in 2 cases, both in group 1 ; and the fifth, sixth and seventh are largest and equal in one instance in group 2.
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From the above it is clear that the largest nerve to enter the plexus is the seventh or eighth in 19 of the 27 cases or in over 70 per cent. (The seventh is largest in 7, the eighth in 6 and the seventh and eighth equally large in 6.)
When we attempt to correlate this with the division of the plexuses into groups, we find that in group 1, in which the fourth cervical nerve enters the plexus, the largest nerve and the point of greatest strength is in the sixth cervical nerve in one case, the seventh in 5 cases, the eighth in 5 cases and the seventh and eighth equally in 7 cases. That is, while all 18 of the above plexuses would be classed as cephalic because of receiving a branch from the fourth cervical nerve, those cases in which the largest nerve is the eighth or seventh and eighth would most surely be classed as postfixed and only those cases in which the largest nerve is the sixth and possibly the seventh would be classed as prefixed. That is, each group would have to be subdivided so that the cephalic plexuses (my group 1) would be subdivided into prefixed, postfixed and intermediate.
The diameter of a nerve depends not only upon the number of nerve fibers but also upon the amount of connective tissue, the amount of fat and the quantity of moisture in it. In making a dissection it is very difficult to tell when all the connective tissue has been removed leaving only that tissue which we call epineurium. There is no line of demarcation between the epineurium and the surrounding connective tissue and different dissectors are not liable to agree as to the dividing line. Furthermore in my series it was impossible to tell if a student had removed the same relative amount of connective tissue from the different nerves. The septa that the epineurium sends through the nerve separating and binding together the bundles of nerve fibers are of greatly varying size and blend to some extent with the perineurium that immediately surrounds the nerve bundles.
In very lean persons there is little fat in the epineurium, but in the fat, there is a very considerable amount, especially in the septa between the nerve bundles. An indication of the amount of variation may be seen in sections of a nerve from a fat and a lean body respectively.
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In the different nerves of the same plexus, there is also some variation in the amount of fat in the epineurium and of the amount of connective tissue forming the epineurium. The amount of moisture is of less moment though without care it might easily happen that the moisture in the different nerves would be unequal.
It is also extremely difficult to be sure that one is getting correct measurements. Very slight pressure against the muscle dorsal to the nerves such as is caused by traction on the limb or permitting it to drop dorsally will cause a very appreciable amount of flattening. In the comparisons given above, I have endeavored to be very careful to eliminate this source of error so far as possible and have verified each measurement several times, but still do not feel confident of the results. It is, of course, easy to see on inspection that all of the nerves in a plexus are not of the same size, some of them are usually markedly larger or smaller than the others. On the other hand, I feel quite sure that the differences between certain of the nerves especially in the center of the plexus are in many cases so small that under slightly altered conditions two different observers might obtain quite opposite results. Taking all these things into consideration, I feel that the method of classifying plexuses as prefixed and postfixed, based upon the size of the nerves, as we are able to determine them, is of very doubtful value, and that for the human plexus it should have Httle or no weight as an accessory to other methods.
ARRANGEMENT OF NERVE BUNDLES IN A NERVE
As is well known, each of the anterior rami of a spinal nerve as it passes out between the muscles is composed of a large number of nerve fibers collected into bundles, funiculi. Each funiculus is surrounded by a more or less definite connective tissue sheath, perineurium. These bundles are bound together by more connective tissue epineurium, which also finally forms a sheath around the whole nerve.
The funiculi in a nerve do not run along parallel with one another but they interlace and divide frequently and the branches
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often join to form new nerve bundles which also usually divide and join again with other branches, and this may be repeated again and again. Where two nerves join, as in a plexus, there is not only a mixing of the nerve bundles of the two but a direct union of the funiculi so that wlien a funiculus from one has joined a funiculus from the other, the newly formed bundle surrounded by perineurium contains a mixed group of fibers from both. There may be a dozen or more bundles in a nerve bound together and surrounded by epineurium. The funiculi vary greatly in size, from minute threads to good-sized bundles. If all the epineurium could be dissected away, it would not be difficult to see how the funiculi branched and how the branches were joined together again. This can be done only with great difficulty if at all in the majority of embalmed bodies. In only a few instances, in selected cases, have I, by means of ordinary dissection been able to remove most of the epineurium and to trace the funiculi to any extent through a plexus. I have found that even with the greatest care in making such a dissection there were many places in which it was impossible not to break some of the fine connecting fascicles. Some of these connecting bundles are so small that it is difficult or absolutely impossible to distinguish them from the connective tissue. I have always felt much doubt as to whether I might ifot have broken without knowing it many of the minute bundles that pass from one funiculus to another. I have, therefore, not included the results of ' any such dissection in my series. Paterson ('96) also feels doubt of his ability to make such dissections, and he says "by anatomical methods it is impossible to separate the fibers of one spinal nerve from its neighbor."
In all of the cases included in this report the dissection has been carried only so far as seemed safe and only so much of the connective tissue has been removed as was possible without danger of tearing the nerve bundles. It was thought best not to attempt to remove all of the peripheral epineurium in an}^ of the cases.
To make out the distribution of the fibers of a given spinal nerve in the branches of the brachial plexus it would be necesary
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to follow these through the funiculi. To do this would necessitate the removal not only of the epineurium but also of the perineurium. I do not believe that this is anatomically possible. Some investigators have apparently been more successful in removing the epineurium and tracing nerve bundles and nerve fibers through the plexus. Their reported results indicate that they were able to follow not only the funiculi but the fibers of a given spinal nerve and that they could make out the distribution of the fibers to the various branches of the plexus.
SEPARATION OF NERVE BUNDLES BY MACERATION
In order to see how far it was possible to remove the connective tissue by chemicals and to trace back the nerves to their elemental constituents, I have experimented with various macerating fluids. That which I found the most satisfactory consisted of 20 parts of strong nitric acid and 20 parts glycerine in 40 parts water. A number of plexuses have been macerated in this fluid. A plexus placed in this macerating fluid was allowed to remain until the connective tissue of the epineurium was soft and pulpy and could be easily removed with a soft camel's hair brush. The nerves were allowed to remain in the fluid 48 hours or more depending on the method by which they had been embalmed and hardened. When the epineurium was sufficiently softened there was a decided shortening in the length of the plexus. This occurred suddenly when the maceration had been carried to a certain stage and not gradually as the maceration progressed. The cause of this contraction I have not been able to explain. When sufficiently macerated so that the epineurium could be easily removed, plexuses may be kept for almost any length of time in strong alum solutions or in 10 per cent formalin. As it is the connective tissue that gives the strength to the nerves they are. after maceration, easily broken and must be handled very carefully. Even if the maceration is continued for a much longer time, it does not soften the perineurium. This remains as a smooth definite sheath around the nerve bundles until with prolonged maceration the whole plexus becomes so pulpified and so softened that it cannot be studied at all. I do not know whether
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the difference in the effect of the nitric acid on the epineurium and the perineurium is due merely to greater density of the latter, or if there is a difference in the kind of connective tissue forming each of them. It is clearly evident that when two funiculi join to form a third, we cannot, by this method, determine whether the branches from this latter contain nerve fibers from one or from both of the original bundles.
Figure 9 shows the principal funiculi of a plexus from which the epineurium has been removed by maceration. From this it will be seen how complicated is the network of bundles and how absolutely hopeless it is to attempt to trace to a definite spinal nerve the elements which enter into some of the branches even when the epineurium has been so completely removed. It will be seen, therefore, how much more difficult, in fact, how impossisible it is to trace these funiculi ; let alone nerve fibers accurately by means of ordinary dissection.
COMBINATION OF NERVES TO FORM A PLEXUS
We have so far been speaking of the brachial plexus, while as a matter of fact we have been dealing only with the nerves which go to make up that plexus. These nerves are usually described as combining to form the plexus in the following manner. The fifth and sixth cervical nerves unite to form a common stem, the cephalic trunk (upper or outer trunk or primary cord) and in the same way, the eighth cervical and first thoracic nerves unite to form a caudal trunk (lower or inner, trunk or primary cord) while the seventh cervical remains single and represents an intermediate trunk (middle, trunk or primary cord). Each of these trunks divides into ventral and dorsal branches. The ventral branches of the cephalic and intermediate trunks join to form a lateral fasciculus (outer cord); the ventral branch of the caudal trunk remains single as the medial fasciculus (inner cord) ; while the dorsal branches of all three trunks join to form the dorsal fasciculus (posterior cord) (figs. 1, 2, 3).
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t
VARIATIONS IN THE FORMATION AND DIVISION OF THE TRUNKS AND OF THE FASCICULI OF THE PLEXUSES
Variations of the above arrangement fall into two main groups. In the first, no true cephalic or caudal trunks are formed but some or all of the nerves divide into dorsal and ventral branches and these combine to form the lateral, medial and dorsal fasciculi, or no true dorsal or lateral fasciculi are formed but branches from the dorsal and ventral rami of the nerves or trunks unite to form the branches of the plexus, or the cephalic and intermediate trunks fail to divide into dorsal and ventral branches but the trunks unite to form a single lateral cord which then divides into dorsal and ventral branches. In all of these variations the fasciculi or their branches receive fibers from the same spinal nerves as they would in the usual arrangement.
There is another group of variations of the plexus in which the lateral fasciculus receives fibers from nerves caudal to the seventh cervical or in which the medial fasciculus receives fibers from nerves cephalic to the eighth cervical nerve. A new element is, in these cases, introduced into either the lateral or medial fasciculus. These therefore are distinctly different than the usual and warrant the subdivision of the groups into subgroups or types. There are only 11 such atypical plexuses or 6.28 per cent of the 175 studied.
We shall consider the first group of variations, dealing with each trunk and fasciculus separately, and shall then consider the subdivision of the plexuses into subgroups.
The cephalic trunk
The cephalic trunk is formed by the union of the fifth and sixth cervical nerves in 157 plexuses or in 89.71 per cent of the 175 plexuses studied. The fourth cervical nerve in all cases where this enters the plexus joins the fifth before this has united with the sixth. In 153 of the 157 cases the cephalic trunk divides into dorsal and ventral divisions, (fig. 1), but in 4 it does not divide but is joined by the intermediate trunk and the nerve cord thus formed then divides into dorsal and ventral divisions (fig. 21).
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This variation is perhaps caused by the dissector removing less than the usual amount of the connective tissue sheath that surrounds the trunks but at the time of the dissection it appeared as if as much had been removed as in other cases.
In 14 plexuses the fifth and sixth cervical nerves divide into dorsal and ventral branches and the ventral branches join to form a cephalo- ventral trunk (fig. 15). In 2 cases the fifth nerve divides into dorsal and ventral branches and the ventral branch joins the sixth nerve to form the cephalic trunk, and in 2 others the sixth nerve divides into dorsal and ventral branches and the ventral branch joins the fifth nerve to form the cephalic trunk. The cephalic trunk in these cases divides into dorsal and ventral divisions in the usual way. These cases are probably caused by the dissector removing more than the usual amount of the connective tissue sheath from around the trunks.
The intermediate trunk
The intermediate trunk is formed by the seventh cervical nerve only in all of the 175 cases. In 164 or 93.71 per cent it ■divides into dorsal and ventral branches (fig. 1). The ventral branch joins the ventral branches from the cephalic trunk or nerves to form the lateral fasciculus and the dorsal division joining the dorsal divisions of the cephalic and caudal trunks or the nerves forming them to form the dorsal fasciculus or its equivalent.
In 5 instances the intermediate trunk divides into 3 parts. In 4 of these, two of the divisions are ventral, one joining the ventral branch of the cephalic trunk to form the lateral fasciculus and the other passing to the medial fasciculus, while the dorsal branch goes into the dorsal fasciculus in the usual way (fig. 4). In the fifth instance there are two dorsal branches both of which go to the dorsal fasciculus, and the ventral branch joins the ventral branch of the cephalic trunk to form the lateral fasciculus. In 4 other plexuses, already' noted in discussing the cephalic trunk, the intermediate and cephalic trunks join before dividing into dorsal and ventral branches (fig. 21). In 2 other cases the dorsal branch of the cephalic trunk joins the
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intermediate trunk before this divides into dorsal and ventral branches (fig". 24).
The caudal trimk
The caudal trunk is formed by the union of the first thoracic and the eighth cervical nerves in 166 of the 175 plexuses or in 95.42 per cent (fig. 1). It then divides into dorsal and ventral divisions in 165 of them. In the other case the caudal trunk divides into the ulnar and the medial head of the median nerve and this gives off a dorsal branch. In 4 of the above 166 cases the eighth cervical nerve before joining the first thoracic gives off a small branch. This joins the lateral fasciculus of the plexus in 2 (fig. 27), the lateral head of the median nerve in 1 (fig. 25) and the ventral division of the intermediate trunk in 1. In 2 of the 166 the caudal trunk, before dividing into dorsal and ventral branches, gives off a small ventral ramus that joins the intermediate trunk in 1 (fig. 6), and the lateral fasciculus of the plexus in the other (fig. 8).
In 6 plexuses, the eighth cervical nerve divides into dorsal and ventral branches. The ventral branch joins the first thoracic nerve to form the medial fasciculus. There is no dorsal branch of the first thoracic (fig. 26). There is no caudal trunk that divides into dorsal and ventral divisions.
In 2 instances, both the eighth cervical and first thoracic nerves divide into dorsal and ventral branches and the ventral branches join to form the medial fasciculus. These and the proceeding 6 cases are perhaps produced by the dissector removing more than the usual amount of the connective tissue sheath, and it is not impossible that nerve fibers may have been broken through although no broken ends were found at the time the plexus was verified.
In one plexus the eighth cervical and first thoracic nerves join to form the caudal trunk which after receiving a branch from the intermediate trunk divides into dorsal and ventral divisions.
The lateral fasciculus of the plexus
The lateral fasciculus of the plexus is formed by the junction of the ventral divisions of the cephalic and intermediate trunks
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in 143 plexuses, or in 81.71 per cent of the 175 studies (fig. 1). In two others, the intermediate trunk, before giving off its ventral division, receives a small additional branch from the caudal trunk. In 3 additional plexuses, the lateral fasciculus is formed in the usual way but receives a small additional branch, in 1 from the caudal trunk (fig. 8) and in 2 from the eighth cervical nerve (fig. 27).
In 2 other plexuses, the arrangement differs from the usual in that the ventral division of the intermediate trunk to the lateral fasciculus is given off after the trunk is joined by the dorsal division from the cephalic trunk (fig. 24). In 4 others the cephalic and intermediate trunks join and this cord then splits into a lateral fasciculus and a branch to the dorsal fasciculus (fig. 21). In the above 6 cases perhaps if more of the connective tissue had been, removed from around the nerve they would have corresponded to the usual type.
In 12 plexuses, the fifth and sixth cervical nerves divide into dorsal and ventral branches and the ventral branches unite to form a cephaloventral trunk which is then joined by the ventral branch of the seventh cervical nerve to form the lateral fasciculus. In 9 of these cases, the fourth cervical nerve joins the fifth before it divides into dorsal and ventral branches.
There are 2 other cases, similar to the above except that the ventral branch of the sixth joins the undivided fifth cervical and the ventral branch of the cephalic trunk thus formed joins the ventral branch of the seventh cervical to form the lateral fasciculus.
In 7 cases there is no lateral fasciculus formed. In 4 of these the ventral brq,nch of the cephalic trunk, and in 2 others a trunk formed by the union of the ventral branches of the fifth and sixth cervical divides into musculo-cutaneous and the lateral head of the median nerve (fig. 15). In 6 of the above this latter is joined by the ventral branch of the seventh cervical (fig. 16). In the other case, the ventral branch of the seventh cervical joins the medial head of the median, it corresponds to the lateral head of the ulnar (fig. 15). In the 21 plexuses just described, it is probable that more of the connective tissue was removed than usual and in the last 7 it is not impossible that small connecting
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funiculi mg^y have been broken, but no evidence of this was found by naked eye examination.
The 7nedial fasciculus of the plexus
The medial fasciculus of the plexus is formed of the ventral branch of the caudal trunk in 166 or in 94.85 per cent of the 175 plexuses (fig. 1). In 5 of these there is a branch from the seventh cervical nerve to the medial fasciculus (fig. 5) .
In 6 specimens the medial fasciculus is formed of the ventral branch of the eighth cervical joined with the whole of the plexus part of the first thoracic which has in these no dorsal branch; it takes the place of the caudal trunk (fig. 26). In one of these the medial fasciculus receives a branch from the seventh cervical nerve (fig. 4).
In 2 others the medial fasciculus is formed b}^ the union of the ventral branches of the eighth cervical and first thoracic nerves. It is not impossible that there would be others arranged like the above if more of the connective tissue could have been safely removed.
There is one other specimen in which the medial fasciculus and the caudal trunk are identical. The medial head of the median in this gives off a dorsal branch to the dorsal fasciculus which is usually given off from the caudal trunk.
The posterior fasciculus of the plexus
The posterior or dorsal fasciculus of the plexus is formed of the dorsal branches of the cephalic, intermediate and caudal trunks, or of dorsal branches from the nerves making up these trunks. It is seldom possible to trace the branches proximally to the spinal nerves. These dorsal branches do not always combine in the same way.
In 10 plexuses (fig. 25) the dorsal branches of all these trunks meet at about the same point to form the posterior fasciculus (fig. 1).
In 86 plexuses the dorsal branches of the cephalic and intermediate trunks join to form a cephalodorsal cord which is joined
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somewhat more distally bj^ the dorsal branch of the caudal trunk (fig. 2). In 2 of these the dorsal fasciculus receives an additional branch or branches. In 1 this comes from the ventral division of the intermediate trunk and is single, in the other it comes from the medial fasciculus and is double. In 5 others, of the above plexuses, one of the branches to the dorsal fasciculus receives an additional branch. This joins the dorsal branch from the cephalic trunk in 3 and comes from the sixth cervical nerve in 2 and from the fifth in 1. It joins the dorsal branch from the intermediate trunk in 1 and arises from the eighth cervical nerve and it joins the dorsal branch from the caudal trunk in 1 and comes from the intermediate trunk. In 2 of the above 86 plexuses the branch from the caudal trunk receives no fiber from the thoracic nerves, but comes from the eighth cervical only.
In two cases the dorsal division of the cephalic trunk joins the intermediate trunk and the cord thus formed divides into dorsal and ventral parts. The dorsal division joins with the dorsal division of the caudal trunk to form the dorsal fasciculus (fig. 24) .
In 9 cases the dorsal branches of the fifth and sixth cervical nerves combine to form a dorsocephalic trunk, the equivalent of the dorsal division of the cephalic trunk; this then joins the dorsal division of the intermediate trunk and more distally is joined by the dorsal division of the caudal trunk.
There is another case exactly like this except that the caudal trunk does not divide into dorsal and ventral branches but after giving off the cutaneous branches splits up into ulnar and medial head of the median nerve and this latter gives off a dorsal branch that takes the place of and is equivalent to the usual dorsal branch of the caudal trunk.
In 26 plexuses the dorsal divisions of the intermediate and caudal trunks join to form a caudodorsal cord which is joined more distally by the dorsal division of the cephahc trunk (fig. 5). In three of these the posterior fasciculus receives an additional branch, in one from the lateral fasciculus, in two from the medial. In one of the above cases the branch from the caudal trunk comes from the eighth cervical only. In one, the dorsal branch of the
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intermediate trunk receives an additional branch from the ventral branch of the cephalic trunk.
In 4 instances the cephalic and intermediate trunks join and the cord thus formed divides into dorsal and ventral branches. The dorsal branch joins with the dorsal division of the caudal trunk to form the posterior fasciculus (fig. 21).
In one case the fifth and sixth cervical nerves divide into dorsal and ventral branches. The dorsal branches unite to form a dorsocephalic cord that joins another cord formed by the union of the dorsal branches of the intermediate and caudal trunks to form the posterior fasciculus. Slightly more distal the posterior fasciculus receives an extra branch from the lateral fasciculus. It will be seen then that the posterior fasciculus is formed by the union of dorsal branches of the plexus in 139 records.
In 36 plexuses or 20.57 per cent of the 175 studied, there is no real posterior fasciculus unless we consider a single nerve, the radial, as representing the dorsal fasciculus.
The arrangement of the dorsal branches in these cases will be described in connection with the discussion of the radial and axillary nerves.
If the epineurium could have been completely removed from all the plexuses, I have no doubt that more of them would have corresponded to this last group in which no real dorsal fasciculus was formed. It will be noted that in all but 6 of the plexuses of this series the caudal branch to the dorsal fasciculus was from the caudal trunk formed by the eighth cervical and the first thoracic nerves. Herringham ('87) found the branch from the first thoracic to the dorsal fasciculus absent in 39 out of 45 cases or in 86.66 per cent. W. Harris ('04) however, found the branch from the first thoracic nerve to the dorsal fasciculus 7 times out of 9. In the specimens studied by maceration in nitric acid, I found that the first thoracic sends branches to the dorsal fasciculus in the majority of instances. As already explained, because of the danger of breaking the minute connections by gross dissection I have attempted to determine in only a few instances whether or not the branch to the dorsal fasciculus from the caudal trunk contained fibers from both the eighth cervical and first
314 ABRAM T. KERR
thoracic. I do not believe that with my material this point could have been determined in the majority of plexuses.
SUBDIVISIONS OF THE PLEXUSES OF GROUPS 1, 2 AND 3
The lateral fasciculus of the plexus or its equivalent contains fibers from the seventh cervical and the nerves cephalic to this and the medial fasciculus contains fibers from the eighth cervical and the nerves caudal to this in 164 or 93.71 per cent of the 175 plexuses studied. Some of the 11 atypical specimens are found in each of the three groups into which the plexuses are divided. In 6 of the 11 atypical specimens there is a brajich from the intermediate trunk (seventh cervical nerve) to join the caudal trunk or the medial fasciculus of the plexus (fig. 4). In the other 5 there is a branch from the caudal trunk or the eighth cervical nerve to join the lateral fasciculus or one of the nerves that go to it (figs. 6 and 8).
The branch to the lateral fasciculus is found in the plexuses of group 1 and 3 but has not been found among those of group 2. The branch from the intermediate trunk to the medial fasciculus has been found among groups 1 and 2.
Schumacher describes in 8 of the 10 cases examined by him a branch from the lateral to the medial fasciculus. He may refer to a branch similar to the one mentioned above from the intermediate trunk to the medial fasciculus or to a branch similar to the lateral head of the ulnar nerve.
It is not improbable that the significance of this branch to the medial fasciculus may be the same as that of the lateral head of the ulnar nerve, although in one case the two coexist. Its sole function might be to bring fibers of the seventh cervical or some nerve cephalic to this to the ulnar nerve.
The lateral head of the ulnar nerve occurs in 75 plexuses or in 42.85 per cent of the 175. Fifty-five of these are in group 1 or 50.00 per cent of the 110 plexuses in the group. Sixteen are in group 2 or 30.76 per cent of the 52 plexuses of this group and 4 are in group 3 or in 30.76 per cent of the 13 plexuses found here. It will be seen then that this also occurs more often in the cephalic group of plexuses. A more detailed description of this lateral
BRACHIAL PLEXUS OF NERVES IN MAN 315
ulnar fasciculus will be given in connection with the ulnar nerve.
Those plexuses within each group in which branches from the seventh cervical (the intermediate trunk) contribute to the medial fasciculus I have classified as cephalic types and those in which a branch from the caudal trunk goes to the lateral fasciculus either directly or by joining the seventh cervical nerve I have classified as caudal types.
Group 1 is in this way subdivided into three subgroups; group 2 into two subgroups, and group 3 into two subgroups. The types in group 1, I have classified A, B, and C. Type B (fig. 1) is the typical arrangement described above. Type A is the most cephalic and type C the most caudal. In all of these in group 1 the fourth cervical nerve sends a branch to the plexus.
Type A
Type A is distinguished by having a ventral branch from the intermediate trunk (seventh cervical nerve) to the medial fasciculus of the plexus so that this contains fibers from the seventh and eighth cervical and first thoracic nerves (fig. 5). The lateral fasciculus contains fibers from the fourth, fifth, sixth and seventh cervical nerves. The plexuses of this type are the most cephalic of the whole series. There are five cases of this type or 2.85 per cent of the 175 plexuses. In one of the cases the branch from the caudal trunk to the dorsal fasciculus is from the eighth cervical nerve alone, so that the dorsal fasciculus has no branch from the first thoracic.
Type B
In type B the lateral fasciculus contains fibers from the fourth, fifth, sixth and seventh cervical nerves and the medial fasciculus fibers from the eighth cervical and first thoracic. There are 101 cases of this type, or 57.71 per cent of the 175 plexuses, that is, more than half the total number of plexuses are of type B (fig. 1).
Type C
Type C differs from the preceding in that there is a branch from the caudal trunk to join the seventh cervical nerve or the
316 ABRAM T. KERR
lateral fasciculus (fig. 6). The lateral fasciculus then receives fibers from nerves caudal to the seventh. The medial fasciculus is formed from the eighth cervical and first thoracic nerve. There are 4 cases of this kind, or 2.28 per cent of the 175 plexuses. In 3 of the 4 cases, the extra branch to the lateral fasciculus comes from the eighth nerve only (fig. 27). In the exceptional instances it arises from the caudal trunk. In this case the branch joins the seventh cervical before it divides into dorsal and ventral branches. In another case the branch joins the ventral branch of the seventh cervical. In the other two cases, the branch goes to the lateral fasciculus directly. In two cases the branch also sends an additional offshoot to the dorsal fasciculus. In both cases where the branch to the lateral fasciculus sends a branch to the dorsal fasciculus there is also another separate branch from the caudal trunk to the dorsal fasciculus.
The subgroups of group 2 I have designated types D and E. They receive no fibers from the fourth cervical nerve.
TijpeD
In tj^pe D there is a branch from the seventh cervical nerve to the medial fasciculus of the plexus (fig. 7). The medial fasciculus is then formed of fibers from the seventh and eighth cervical and first thoracic nerves and the lateral fasciculus from the fifth, sixth and seventh cervical. This type is exactly like type A except for the absence of the branch from the fourth cervical nerve. There is only one case of this type or 0.57 per cent.
Type E
In type E the lateral fasciculus is formed of fibers from the fifth, sixth and seventh cervical nerves and the medial fasciculus of branches from the eighth cervical and first thoracic nerves (Fig. 2). The plexuses of this type are exactly like the plexuses of type B except that the branch from the fourth cervical nerve does not join them. There are 51 plexuses of this type or 29.14 per cent of the 175 plexuses.
Group 3 plexuses were divided into tj^pes F and G. The whole of the fifth cervical does not contribute to this type.
BRACHIAL PLEXUS OF NERVES IN MAN 317
TypeF
In type F the lateral fasciculus is formed of branches from the fifth, sixth and seventh cervical nerves and the medial of branches from the eighth cervical and first thoracic nerves (fig. 3). The plexuses of this type are exactly like those of types B and E except that the whole of the fifth cervical nerve does not enter the plexus. There are 12 plexuses of this type or 6.85 per cent of the 175. In one of the plexuses that I have classified as belonging to this type there is a small branch from the fourth cervical nerve to the fifth, in addition to the branch from the fifth to the fourth (fig. 21). This latter branch is larger than the branch from the fourth to the fifth, and I have therefore considered the plexus as belonging to group 3, type F. Types B, E, and F correspond to the type and differ from one another exactly as groups 1, 2 and 3 differ, that is, B receives a branch from the fourth and E does not, and in F the fifth cervical sends a branch to the fourth.
TypeG
In type G there is a branch from the caudal trunk to the lateral fasciculus (fig. 8), just as there is in type C. Types C and G differ from one another in that in C there is a branch from the fourth cervical entering the plexus and in G there is no such branch but there is a branch from the fifth to the fourth cervical nerve. There is only 1 case of this kind making 0.57 per cent of the 175 plexuses studied.
SYMMETRY AND ASYMMETRY ON THE TWO SIDES OF THE BODY
As already pointed out a considerable number of the plexuses of my series were from only one side of the body. There are, however, 63 bodies in which there are satisfactory records for both sides. In 39 of these, or 61.90 per cent of them, the type of plexus is the same on both right and left sides, while in the remaining 24 the type of plexus is asymmetrical.
In these I have tried to determine if the asymmetry is more frequently found in white or colored, in male or female bodies.
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318 ABRAM T. KERR
"WTiere asymmetry occurred I have tried to determine if this is more common among one type of plexus than another, or if sex or color influences it ; also if one type of plexus is found more often on one side of the body than the other.
Symmetry in males and females, white and colored
There are 25 male bodies in which the plexuses on both sides are of the same type, or 62.50 per cent of the 40 male bodies.
There are 15 male bodies in which the type of plexus is asymmetrical, or 37.50 per cent.
There are 14 female bodies in which the plexuses on both sides are of the same type, or 60.86 per cent of the 23 female bodies. In 9 female bodies the plexuses on the two sides are of different types or 39.13 per cent.
There are 18 white bodies with symmetrical plexuses and 14 in which they are asymmetrical, or 56.25 per cent of the 32 white bodies have symmetrical plexuses and 43.75 per cent have the plexuses asymmetrical.
There are 21 colored bodies in which the plexus is of the same type on the right and left sides, or 67.74 per cent of the 31 colored bodies. In 10 colored subjects or 32.25 per cent, the plexuses are asymmetrical.
From the above it will be seen that symmetry is more common than asymmetry in about the ratio of 3 to 2. It would appear also to be very slightly, 1.64 per cent, more common in males than in females.
Symmetrical arrangements of plexuses was more common in the colored than in the whites by about 11.5 per cent.
There are 13 white males with asymmetrical arrangement of the plexuses, or 54.16 per cent of the 24 white males, and 11 or 45.83 per cent in which the type of plexus is different on the two sides of the body. There are 12 colored males with symmetrical and 4 with asymmetrical plexuses or 75 per cent and 25 per cent respectively of the 16 colored males. Symmetry is found in 3 cases to every one in which there is asymmetry among the colored males.
BRACHIAL PLEXUS OF NERVES IN MAN 319
There are 5 white female bodies with symmetrical arrangement and 3 with asymmetrical, or 62.50 per cent symmetrical and 37.50 asymmetrical among the 8 white females. In the 9 colored female bodies, there is a symmetrical arrangement and in 6, or 60 per cent and in 40 per cent, an asymmetrical. This gives a ratio of 3 to .2 among the colored females.
A symmetrical arrangement was found most often among colored males, least often among white males, and more often among white than among colored females. The ratio of symmetry to asymmetry was in colored males 3 to 1, in colored females, 3 to 2. Symmetry was 8.33 per cent more common than , asymmetry in white males and 25 per cent more common in w^hite females.
Symmetry as, regards the type of plexus
Among the 63 bodies where I have satisfactory records from both sides of the body there are only 4 in which the type A plexuses are found. All are asymmetrical. In two of them type A is on the right side, 1 white male and 1 white female. In two, type A is on the left, both in colored females. It is interesting to note that in both the cases where the B type of plexus is on the right side there is a lateral head to the ulnar nerve on this side. In the cases where the B type is on the left side, there is no such branch.
There are 76 plexuses of the B type and in 54 of these it occurred on both sides of the body, or in 71.05 per cent. In the 22 bodies in which the B type is found only on one side, the A type is found on the other side in 4, 2 right and 2 left, type C is on the left in 2, the E type is on the left in 7 and on the right in 6, and the F type on the left in 3. It will be noted then that in 14 of the above the B type is on the right and in 8 on the left or nearly 2 to 1.
There are 2 records of C type plexus both on the left side of white malfes and the type B plexus is on the right.
There is but one record of type D. This is on the left of a white male and the type E plexus is on the right.
320 ABRAM T. KERR
There are 33 plexuses of the E type, 18 of these are on both sides of the body, or in 54.54 per cent. The remaining 15 plexuses of the E type are 8 on the right and 7 on the left. Those on the right are associated in 6 cases with B, in 1 with D, and in 1 with F type of plexus on the left. In the 7 instances in which the E type is on the left, the B type is on the right.
Of the 10 plexuses of the F type 6 are found on both sides or 60 per cent. The other 4 cases are associated with B type on the right in 3 and E type on the right in 1.
Symmetry occurs only in the B, E and F types of plexus, which are the most common and typical plexuses for each of the three groups, 1, 2 and 3. This is suggestive that the A, C and D types of plexus are anomalous and ma}^ have no great significance. There is no plexus of the G type in the bodies where the records for both sides are complete. It will be noted that when the A, C or D type of plexus occurs qn one side it is associated with a plexus in the same group on the other side, A and B, B and C, E and D.
Slightly over 71 per cent of the B type plexuses are symmetrical, 60 per cent of the F type and a little over 54 per cent of the E type. That is, in the most cephalic group of plexuses symmetry occurs most often and in the intermediate group least often.
Among the 24 bodies with an asymmetrical arrangement of the plexus, a more cephalic type is found upon the right side in 15 or 62.50 per cent and a more caudal type in 9 or 37.50 per cent.
Among the 24 bodies with asymmetrical plexuses, group 1 is found on one side and group 2 on the other in 13 instances or 54.16 per cent. In these type B of group 1 is on the right side in 7 and type E of group 2 on the left. In the other 6 cases, the arrangement is reversed. In 3 others or 12.50 per cent group 1 is on the right side and group 3 on the left. In these type B of group 1 is on the right and type F of group 3 on the left. In another instance group 2 is on one side and group 3 on the other. In this case type E of group 2 is on the right and type F of group 3 on the left. The remaining 7 bodies were classed as asym
BRACHIAL PLEXUS OF NERVES IN MAN 321
metrical because different types of plexus are found on the two sides but both types are in the same group. Six are in group 1 and 1 in group 2. Of those in group 1, in 4 type A is on one side and type B on the other. In 2 of these type A is on the right and in 2 it is on the left. In two bodies type B is found on the right, type C upon the left. In the case where both plexuses are in group 2, type E is on the right and type F on the left.
THE ORIGIN OF THE BRANCHES FROM THE BRACHIAL PLEXUS
As will be seen from figures 1 to 8 some of the branches of the plexus arise from the rami of the spinal nerves forming the plexus, some from the cephalic and caudal trunks and some from the medial, lateral, and posterior fasciculi. In my study of the nerves of the plexus, the trunks and fasciculi were not broken up and subdivided so that one could see just which spinal nerve contributed to each branch, and as demonstrated by my maceration experiments, this is impossible in a great many cases even by this method, let alone by dissection. It is assumed then that if a nerve arises from a trunk formed by branches from two or more spinal nerves that both or all of them may send fibers to the nerve. It is recognized, of course, that in some cases only one of the nerves may contribute to a branch, but there is no way of determining by anatomical methods when this occurs or which nerve it is. It seems best, therefore, to consider all of the nerves that help to form a trunk or fasciculus as potential elements in each branch from the trunk or fasciculus.
In the usual descriptions, the lateral fasciculus is said to terminate by dividing into the musculocutaneous nerve and the lateral head of the median nerve; the medial fasciculus by dividing into the ulnar nerve and the medial head of the median nerve; the posterior fasciculus by dividing into the axillary and radial nerves. It has already been shown that this does not always occur but I shall not deal separately with the percentage occurrence of this division of each of these fasciculi into medial and lateral branches but shall consider it in connection with each of the branches.
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THE ULNAR NERVE
The ulnar nerve is usually described as arising from the medial fasciculus of the plexus, and the medial fasciculus of the plexus is usually stated to be formed by the junction of the eighth cervical and first thoracic nerves and also at times to receive fibers from the second thoracic nerve.
In my series, the ulnar nerve is formed by the division of the medial fasciculus of the plexus into ulnar nerve and medial head of the median nerve, in 170 of the 175 plexuses studied, or in 97.14 per cent (figs. 1-8).
In 5 instances, the ulnar nerve arises from a trunk formed by the union of the medial fasciculus of the plexus with the whole or a part of the lateral fasciculus. In 3 of these the trunk formed by fusion of the medial and lateral fasciculi of the plexus almost immediately breaks up into the ulnar, median, and musculocutaneous nerves (fig. 27). In the other 2 cases, the lateral head of the median joins the medial fasciculus of the plexus and the trunk thus formed divides into ulnar and median nerves (fig. 28).
The lateral head of the ulnar nerve
In some of the 170 plexuses in which the ulnar nerve arises by division of the lateral fasciculus of the plexus, the nerve receives on its lateral side an additional branch. This has been named the lateral head of the ulnar nerve, caput laterals nervus ulnaris (figs. 1, 2, 3, 10). This lateral head of the ulnar nerve has been figured and mentioned at intervals for a long time by various authors.
The size of the lateral head of the ulnar nerve is subject to much variation, ranging from a minute thread to a good sized branch, as large as the usual medial antibrachial cutaneous nerve. It is often small and pierces or crosses the medial head of the median nerve. There it is intimately bound up in the connective tissue sheath of the latter so that its relation to the ulnar nerve is easily overlooked. In separating the ulnar from the median nerve in dissection, the connection of the lateral head of the ulnar, if not particularly looked for, is often broken.
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Walsh ('77) personally examined 350 plexuses and entirely overlooked this branch in the first 60 but once his attention was directed to it he found it absent in only 25 of the remaining 290.
The dissections in my series were made by students who were not especially looking for a lateral head of the ulnar nerve, and although the work was carefully done I feel quite confident that in a number of cases there had been a lateral head to the ulnar which could not be demonstrated at the time the plexus was examined by • the investigator since the connection with the ulnar had been broken in the dissection and the broken ends could not be found.
In some of these cases there remains a branch connecting with the medial head of the median nerve and similar in all respects to a lateral head of the ulnar nerve except that the connecting fibers could not be demonstrated (fig. 34). There are 30 such cases in my series. Walsh, however, found but 10 instances in which a similar branch failed to send fibers to the ulnar nerve but ended exclusively in the medial head of the median nerve.
There are 8 other instances in which there is a branch which joins the medial fasciculus of the plexus close to the point where this divides into the ulnar and the medial head of the median nerve. I have not been able to prove in these 8 cases that fibers from this branch go to the ulnar nerve, but this is probably the lateral head of the ulnar nerve since in all other similar cases I have found by very careful dissection or by macerating the plexuses in nitric acid that this branch sends fibers to the ulnar nerve. Sometimes all of its fibers go to the ulnar nerve and sometimes part to the ulnar and part to the medial head of the median nerve. I therefore believe this branch always represents the lateral head of the ulnar nerve and have so considered it in this paper. In 6 of the above cases this branch arises from the lateral fasciculus of the plexus (fig. 11) and in 2 from the seventh cervical only.
The lateral head of the ulnar nerve, in my series, passes, in 40 cases, as a single branch to the ulnar nerve (fig. 2), but in 28 cases it divides and sends one or more branches to the medial
324 ABRAM T. KERR
head of the median (fig. 3). In the 8 in which it passes to the medial fasciculus, the ulnar alone, or both ulnar and median nerves may be supplied by it. The fibers which pass to the medial head of the median are usually collected into a single fasciculus (figs. 1, 3, 8) but in a few cases they are divided into 2 or more small branches (fig. 14).
In its course to the ulnar nerve the lateral head of the ulnar in some cases passes dorsal to the medial head of the median (fig. 1), in a few it passes ventral to the medial head of the median, but in the most usual arrangement, it pierces the medial head of the median (figs. 2, 3 and 8).
In my series the lateral head of the ulnar arises from the lateral fasciculus of the plexus in 40 cases (figs. 1 and 3), in 3 of these it passes to the medial fasciculus of the plexus close to its division into the ulnar nerve and medial head of the median nerve (fig. 11), in 13 to the ulnar nerve only (fig. 13), and in 24 to the medial head of the median nerve as well as to the ulnar (figs. 1 and 3). In 2 of these instances the lateral head of the ulnar gives also a branch to the lateral head of the median (fig. 24) .
The lateral head of the ulnar nerve arises from the seventh cervical nerve in 13 cases, in 2 of these passing to the medial fasciculus of the plexus, in 3 to the ulnar nerve only and in 8 to the medial head of the median nerve as well as to the ulnar nerve (fig. 10). In 4 of these the lateral head of the median nerve is formed in the usual way but in the other 4 it is irregular as described in connection with the median. In 2 of these the seventh cervical forms the lateral head of the median nerve (fig. 17), so the lateral head of the ulnar in these instances arises from the lateral head of the median.
In 22 cases the lateral head of the ulnar arises from the lateral head of the median nerve, in 21 of these it passes to the ulnar only (fig. 2), in one case to both the ulnar and the medial head of the median nerve (fig. 8) .
In the series reported by Walsh the lateral head of the ulnar arose proximal to the middle of the lateral fasciculus of the plexus in 15G plexuses, in the rest more distally, in 30 arising from the lateral head of the median nerve.
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The lateral head of the ulnar nerve is found in 75 of the 175 plexuses of my series or in 42.85 per cent of them. Fifty-five of these, or 31.42 per cent were group 1 plexuses, 16 or 9.4 per cent were group 2 plexuses and 4 or 3.4 per cent were group 3 plexuses. The lateral head of the ulnar nerve is found in 55 of the 110 plexuses of group 1 or in 50 per cent of them, in 16 of the 52 plexuses of group 2 and in 4 of the 13 plexuses of group 3 or 30.76 per cent of the group in each of these. If, however, we entirely disregard the 30 doubtful cases in which a similar branch has not been proved to join the ulnar but ends in the medial head of the median nerve (fig. 20), we have a lateral head of the ulnar occurring in 75 out of 145 cases or in 51.72 per cent of the cases examined. If, on the other hand, we consider this branch to the medial head of the median as representing the lateral head of the ulnar, which I believe in the majority of cases it does, we have a lateral head of the ulnar occurring in 105 of the 175 plexuses or 60.00 per cent, which I believe to be more nearly the true percentage.
Walsh ('77), in an examination of 290 plexuses, found the lateral head of the ulnar nerve absent in but 25 cases and in 13 of these there was in place of it a branch arising from the seventh cervical nerve above the clavicle which joined the medial fasciculus of the plexus high up in the axilla.
Spinal nerves that send fibers to the ulnar nerve
The ulnar nerve probably, in all cases, receives fibers from the eighth cervical and first thoracic and in those cases where the second thoracic enters the plexus the possibility of this nerve sending fibers to the ulnar nerve cannot be excluded.
Besides the eighth cervical and first thoracic (or first and second), fibers from the seventh cervical nerve may enter the ulnar nerve in plexuses of types A and D. For, as has been shown, fibers from the seventh cervical nerve pass to the medial fasciculus of the plexus through the branch which is the distinguishing characteristic of these types, and since the ulnar nerve arises from the medial fasciculus, we cannot be sure that the seventh cervical nerve does not take part in its formation.
326 ABRAM T. KERR
Through the lateral head of the ulnar there is brought to the ulnar nerve fibers from the seventh cervical nerve and, in cases where the branch arises from the lateral fasciculus of the plexus or from the lateral head of the median nerve, the possibility of fibers from the sixth, fifth and fourth cervical nerves, one or all, entering the ulnar nerve cannot be excluded. Since this branch brings to the ulnar nerve fibers from the seventh cervical nerve, we might expect to find it absent in those cases in which these fibers may be obtained in another way, for example, in those cases in which the seventh cervical nerve sends a branch to the medial fasciculus of the plexus as in plexuses of types A and D. In 5 of the plexuses of these two types there is no lateral head to the ulnar nerve. In one plexus of type A, there is however also a lateral head to the ulnar nerve (fig. 12), but in this case it arises from the lateral fasciculus of the plexus and may contain fibers from some of the nerves cephalic to the seventh cervical. It is suggestive that the branch from the seventh cervical nerve to the medial fasciculus in the 6 plexuses of types A and D represents the lateral head of the ulnar arising more proximally than usual although in three of the 6 instances the fibers of the seventh cervical nerve cannot be excluded from one of the other branches of the plexus.
In the 5 atypical cases in which the medial fasciculus joins the lateral or the lateral head of the median before the ulnar nerve is given off, the ulnar may receive fibers from any of the nerves cephalic to the eighth cervical. If we disregard the 30 . cases in which a branch similar to the lateral head of the ulnar is present but ends in the medial head of the median nerve and that I have considered as a possible broken branch, we have 145 plexuses in which the record is positive. Among these the ulnar nerve is formed of fibers of the eighth cervical and first thoracic nerves in 61 or 42.06 per cent and of fibers from the seventh and eighth cervical and first thoracic in 16 or 11.03 per cent. In the remaining 68 cases or 46.89 per cent the ulnar has a lateral head that comes from the lateral fasciculus of the plexus, or from the lateral head of the median, and it is not possible to say if the fibers are from the seventh cervical alone
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and that there may not be fibers from the nerves cephaHc to the seventh cervical. The 5 cases in which the lateral fasciculus does not give off the ulnar until after it has joined the medial fasciculus or the medial head of the median are included here also.
There are 92 satisfactory records of the ulnar nerve among the group 1 type of plexus. In 52 of these or 57.28 per cent of the group the fourth, fifth, sixth, seventh and eighth cervical and the first thoracic nerves may take part in the formation of the ulnar nerve. In eleven cases, 11.95 per cent of the group, the seventh and eighth cervical and first thoracic nerves may send fibers to the ulnar nerve and in 29 plexuses, 31.52 per cent of the group, the eighth cervical and first thoracic only send fibers to the ulnar nerve.
There are 47 satisfactory records of the ulnar nerve among the plexuses of group 2. In 14 of these, 29.78 per cent of the group, the fifth, sixth, seventh and eighth cervical and first thoracic nerves may take part in the formation of the ulnar nerve. In 4 cases, 8.51 per cent of the cases, the seventh and eighth cervical and first thoracic alone may send fibers to the ulnar nerve and in 29 plexuses, 61.70 per cent of the group, the eighth cervical and first thoracic nerves alone may send fibers to the ulnar nerve.
There are 6 satisfactory records of the ulnar nerve among the group 3 plexuses. In 2 of these, 33.33 per cent of the group, the fifth, sixth and seventh cervical nerves in addition to the eighth cervical and first thoracic nerves may take part in the formation of the ulnar nerve. In 1 case, 16.66 per cent of the group, the seventh and eighth cervical and first thoracic nerves send fibers to the ulnar nerve and in 3 plexuses, 50 per cent of the group, the eighth cervical and first thoracic nerves alone make up the ulnar nerve.
It will be seen from the above that in the most cephalic group of plexuses there is a relatively greater percentage of the group in which in addition to the eighth cervical and first thoracic nerves, the fourth, fifth, sixth and seventh cervical nerves may also take part in the formation of the ulnar nerve and in the more caudal type, that is, groups 2 and 3, a relatively greater
328 ABRAM T. KERR
percentage of each group in which only the eighth cervical and first thoracic nerves enter and the more cephalic nerves take no part in the formation of the ulnar nerve.
Wichmann ('00) has tabulated from the notes of Renz the reports of 24 writers on 171 cases, showing the spinal nerves that contribute to the formation of the ulnar nerve. ^ Since then, Schumacher ('08) has reported on 10 more investigated by him. If my 145 plexuses are added to these we have a total of 326 cases.
The eighth cervical and first thoracic contribute to the ulnar nerve in 103 cases or 31.28 per cent, Wichmann 41, Schumacher 1, Kerr 61.
The seventh and eighth cervical and first thoracic nerves send fibers to the ulnar nerve in 114 cases or 35.27 per cent, Wichmann 89, Schumacher 9, Kerr 16.
In addition to the eighth cervical and first thoracic nerves the ulnar may receive a contribution from the fifth, sixth and seventh cervical nerves in 87 cases or in 26.68 per cent, Wichmann 19, Kerr 68. The fourth cervical nerve also cannot be excluded in 52 of these from my series.
In Wichmann's tabulation there are 22 additional cases in which the ulnar nerve is formed in some other way. It arises from the eighth cervical nerve in 3 instances, from the seventh and eighth in 3, from the sixth, seventh and eighth in 10 and from the fifth, sixth, seventh and eighth in 6.
From the above it will be seen that the ulnar nerve receives fibers from one or more of the nerves cephalic to the eighth cervical in 220 plexuses or in 67.48 per cent of the 326 cases. In the above tabulation I have excluded the 31 cases in which there is a branch to the medial head of the median. In some of these I feel sure the ulnar also receives fibers from this branch.
JTHE MEDIAN NERVE
The median nerve is usually described as formed by the union of two branches, one from the medial and one from the lateral fasciculus of the brachial plexus, the medial and lateral
In Wiohinann's tabulation he has credited Walsh 101 cases, 27 of these are apiiarentl}' erroneously credited and should have been credited to some one else.
BRACHIAL PLEXUS OF NERVES IN MAN 329
heads of the median nerve respectively. It will thus be seen that the nerve may contain fibers from all the spinal nerves entering the plexus.
In 150 of the 175 plexuses of my series, the median nerve is formed in the usual way by two heads, as described above (fig. 5) . The lateral head arises from the lateral fasciculus of the plexus which is formed by the union of the ventral branch of the cephalic trunk with the ventral branch of the intermediate trunk (figs. 1, 2, 3). There are two other plexuses differing from the above only in that the lateral fasciculus of the plexus from which the lateral head arises receives fibers from the caudal trunk of the plexus. One of these plexuses belongs to type C (fig. 6), and the other to type G of plexus (fig. 8). Th^re are then 152, or 86.85 per cent, of the 175 plexuses of my series in which the median nerve may be considered to arise by two heads in the usually described manner.
In the remaining 23 plexuses of the series, the median nerve is formed in a different way.
In 7 of these instances, the lateral head of the median is formed by the ventral branch of the cephalic trunk, after giving off the musculocutaneous nerve, joining with the ventral branch of the intermediate trunk (seventh cervical nerve) (fig. 18). In another case, the ventral branch from the intermediate trunk joins the medial head of the median, giving off also the lateral head of the ulnar, (fig. 15), but sending no branch to the medial head of the median. In three of the above cases, the branch from the seventh cervical nerve divides and goes to the medial head of the median as well as helping to form the lateral head (fig. 16). In one of these latter there is an additional branch to the medial head of the median nerve from the ventral division of the seventh cervical nerve, which gives off also from its dorsal division the lateral head of the ulnar nerve, and this also connects with the medial head of the median.
There is a ninth plexus in which the lateral head of the median nerve arises from the ventral branch of the intermediate trunk (seventh cervical nerve) of the plexus. The ventral branch of the cephalic trunk (fifth and sixth cervical nerves) does not con
330 ABRAM T. KERR
tribute to the formation of the median in the axilla but forms a large nerve which, after giving off three branches to the coracobrachialis muscle, divides into two branches. These pierce the coracobrachialis muscle separately, one becomes the musculocutaneous and the other joins the median nerve about the middle of the arm (fig. 17). The median nerve beyond this point may contain fibers from all the spinal nerves which contribute ordinarily to its formation. The lateral head of the ulnar in this case arises from the lateral head of the median (seventh cervical) and sends branches to the medial head of the median as well as to the ulnar nerve.
In 3 of the remaining 14 plexuses, the medial and' lateral fasciculi of the plexus join to form a common stem that immediately splits up into median, ulnar and musculocutaneous nerves (fig. 27).
In two instances, the ulnar and median nerves arise from a common stem formed by the union of the lateral head of the median with the medial fasciculus of the plexus. Almost immediately after this stem is formed it divides into median and ulnar nerves (fig. 28). The above five cases have already been noted in discussing the ulnar nerve.
In 9 cases, the musculocutaneous nerve does not separate from the lateral fasciculus of the plexus, but the lateral fasciculus of the plexus joins the medial head of the median nerve to form a common stem. This passes down the arm and gives off the musculocutaneous nerve as a single definite nerve in 6 instances (fig. 6), but as a number of separate branches in 3 instances.
There were a number of other instances in which there were interesting interrelations between the median and the musculocutaneous nerves. Some of these will be considered in the description of the musculocutaneous nerve.
Of the 152 plexuses in which the median nerve arises by two heads in the usual way, 72, or 47.36 per cent neither receive nor give off any branches (figs. 5 and 7). But in the remaining cases one or the other of the heads of the median nerve either receive or give off branches.
The medial head of the median receives an additional branch
BRACHIAL PLEXUS OF NERVES IN MAN 331
in 54 instances, or 35.52 per cent. In 10 cases this branch comes from the seventh cervical nerve, in 4 of them dividing and sending a subdivision to the uhiar nerve as the lateral head of the ulnar (fig. 10), and in 6 of them remaining undivided (fig. 19).
In 40 of the cases, the branch to the medial head of the median arises from the lateral fasciculus of the plexus. In 24 of these the branch divides into two parts sending one of the subdivisions to the ulnar nerve as the lateral head of the ulnar (figs. 1 and 3). In 1 of these instances it divides into three branches, one going to the ulnar, one to the lateral head of the median, and the third to the medial head of the median nerve, in one of these giving off in addition a branch to the coracobrachialis muscle (fig. 24) , In another of the above instances, the lateral head of the ulnar, in addition to sending fibers to the ulnar and medial head of the median, gives off two branches that join the lateral head of the median. In a third case, in addition to a lateral head of the ulnar as above, there is an additional branch from the lateral fasciculus to the medial head of the median.
In 16 instances, the extra branch to the medial head of the median does not divide but goes to the medial head of the median only (fig. 20). In the 4 remaining instances, the branch to the medial head of the median nerve arises from the lateral head of the median, in 1 giving off the lateral head of the ulnar (fig. 8), and in 2 going to the medial head of the median only (fig. 21), and in 1 sending a branch to the lateral head as well as the medial head of the median nerve.
In only one instance is there a branch given off from the medial head of the median nerve. This branch goes to the coracobrachialis muscle (fig. 4), and may receive its fibers from the seventh cervical nerve since there is a branch from this to join the medial fasciculus of the plexus from which the medial head of the median nerve arises.
The lateral head of the median gives off a lateral branch or branches in 26 plexuses, 4 of these have already been noted where this branch goes to the medial head of the median. In 20 of the remaining 22 instances, the branch connects with the ulnar nerve as the lateral head of the ulnar, as in figure 2. In one
332 ABRAM T. KERR
of these there is given off from the lateral head an additional branch that goes to the coracobrachialis muscle (fig. 22). In another instance the lateral head of the median gives off a branch which was said to be the lateral head of the ulnar but the nerve was broken and could not be verified. In the other case the branch supplies the coracobrachialis muscle.
The lateral head of the median nerve in five instances receives a branch. In one of these it is from the seventh cervical nerve (fig. 23). As already noted above, this branch comes from the lateral fasciculus of the plexus in two instances. In one case, the lateral head of the median receives a branch from the eighth cervical nerve (fig. 25), and in another from the medial fasciculus of the plexus (fig. 26).
From the above it will be noted that the lateral head of the median gives off branches in 26 instances but that it receives them in only 5 ; the medial head of the median gives off a branch in but one instance while it receives branches in 54. The tendency is therefore, in the great majority of cases, for the branches here to pass from the lateral toward the medial side of the plexus.
The median nerve received fibers from the fifth, sixth, seventh and eighth cervical and first thoracic nerves in 116 of the 136 cases reported by Wichmann from the literature. Schumacher has added 7 cases in which the above five nerves sent fibers to the median. In other words, if we disregard the fourth cervical nerve, which is not accounted for by these authors, all of the nerves which form the brachial plexus contribute to the formation of the median nerve in 123 of the 146 cases listed by them'. In the remaining 23 cases, the fifth cervical nerve failed to send a branch to the median in 10 instances in Wichmann's series and in 2 of Schumacher's. The first thoracic nerve failed to send a branch to the median in 7 of Wichmann's and 1 of Schumacher's cases. Wichmann reports 3 instances in which other cervical nerves were lacking in the median, in one case it was the fifth and sixth cervical nerves, in one case the sixth cervical nerve and in one the eighth cervical nerve.
In none of the 175 plexuses of my series, was it possible to be
BRACHIAL PLEXUS OF NERVES IN MAN 333
sure from the dissection that any of the nerves which go to make up the brachial plexus did not enter the median nerve. I am, however, reasonably certain that all of them do not contribute in all instances but I have complete records of so few macerated plexuses that I hesitate to quote statistics, since in only 1 of them was there a nerve lacking, the fifth cervical in this case.
If we assume then that in the other instances of my series all of the nerves that make up the brachial plexus enter the median nerve, we have 174 records. When these are added to the 123 instances recorded by Wichmann and Schumacher, we have 297 instances in which the fifth, sixth, seventh and eighth cervical and first thoracic nerves send fibers to the median nerve, or 92.52 per cent of the 321 records.
THE MUSCULOCUTANEOUS NERVE
The musculocutaneous nerve is usually described as formed by the division of the lateral fasciculus of the brachial plexus into the lateral head of the median nerve and the musculocutaneous nerve.
Since the nerve or nerves to the coracobrachialis muscle so frequently arise from other sources than the musculocutaneous, I have described the branch or branches to this musele separately, and I have regarded the musculocutaneous nerve as complete whether or not it gave off these branches.
Among the 175 plexuses of my series, the musculocutaneous nerve arises by division of the lateral fasciculus of the plexus into medial head of the median nerve and musculocutaneous nerve in 155 cases, or 88.57 per cent (fig. 1). In two of these the lateral fasciculus of the plexus receives a branch from the eighth cervical nerve. These are of the type C of plexus (fig. 28). In another case the lateral fasciculus receives a branch from the medial fasciculus of the plexus, type G of plexus (fig. 8) . In these three cases we cannot be sure that the eighth cervical nerve does not send fibers to the musculocutaneous nerve and in the last instance the first thoracic may also. In one of the above 155 cases the musculocutaneous is not complete but the major portion of it arises from the lateral fasciculus and the
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branch which suppHes the biceps muscle comes from a loop in the first part of the median nerve. In another of the 155 cases the lateral fasciculus does not divide as usual but the whole of it forms the musculocutaneous nerve, the lateral head of the median nerve being derived from the seventh cervical. In the arm, the musculocutaneous nerve sends a branch to the median nerve in this case (fig. 17).
There are three plexuses, 1.71 per cent of the 175, in which the musculocutaneous nerve arises from a trunk formed by the union of the medial and lateral fasciculi of the plexus (fig. 27). This trunk divides into median, ulnar and musculocutaneous as previously noted in connection with these other nerves. There are 9 instances, 5.14 per cent of the 175, in which the lateral fasciculus of the plexus joins with the medial head of the median and from the trunk thus formed the musculocutaneous nerve arises as a single branch (if we ignore the branch to the coracobrachialis) in 6 (fig. 6), and in two or more branches in 3 cases. In the above 12 plexuses the eighth cervical and the first thoracic nerves may send fibers to the musculocutaneous nerve.
In 9 of the above cases in which the musculocutaneous arises from a stem common to it and to the median or median and ulnar, there are records for both sides of the body and in all of these the arrangement on the other side was normal. Testut ('84) found the musculocutaneous fused with the median in 6 instances out of 105.
There are 8 plexuses, 4.75 per cent of the 175, in which the musculocutaneous nerve arises from the ventral division of the cephalic trunk of the plexus (figs. 15 and 16). In these cases, the seventh cervical nerve can take no part in the formation of the musculocutaneous nerve unless the musculocutaneous receives fibers of the seventh through its branches in the arm from the median or some other nerve. My records are complete through the arm for only 3 of these cases and these show no branches from the median to the musculocutaneous nerve but on the other hand in one of the plexuses there is a branch from the musculocutaneous to the median nerve.
My records for the musculocutaneous nerve are complete
• BRACHIAL PLEXUS OF NERVES IN MAN 335
through the arm for only 75 plexuses, in 18 of these the musculocutaneous nerve gives off a branch to the median nerve. (In one of these instances the musculocutaneous arises from the cephalic trunk formed only by the fourth, fifth, and sixth cervical nerves). In one of the above instances, the musculocutaneous also receives a branch from the median nerve.
In addition to these, in one of the plexuses where the musculocutaneous nerve arises from the median nerve as described above, it gives off a branch which joins the median nerve further distad. This branch arises from the median nerve distal to the point where the musculocutaneous would normally pierce the coracobrachialis muscle which it does not pierce in this case.
Although these records show that in nearly a quarter of the plexuses the musculocutaneous nerve gives off a branch in the arm which joins the median nerve, I do not believe that such a relation exists as frequently as this, for undoubtedly some of the records were made because of the occurrence of this anomaly. On the other hand, in 100 plexuses of my series the records were not preserved for the arm so that I cannot be positive that there may not have been more cases where the communication existed. If there were no more instances among the 175 plexuses of my series, which is unlikely, the anomaly is found in this series in 10.28 per cent of the 175. In the 75 where the records are complete, it is found in 18 or in 24 per cent of the cases. The truth probably lies somewhere between these two extremes.
Testut ('84) found a branch from the musculocutaneous nerve to the median nerve in 38 instances out of 105 examined, or 36.19 per cent, which is considerably larger than in my series.
In 3 cases, or in 4 per cent of the 75 complete records, the median nerve in the arm sends a branch to the musculocutaneous nerve. In one of these, as already noted, the median also receives a branch from the musculocutaneous. Testut, found a branch from the median to the musculocutaneous nerve in only two out of 105, or in less than 2 per cent, while Villar ('88) found such a branch in 3 out of 37 cases, or in 8.10 per cent.
In my series of 175 cases, the musculocutaneous nerve may receive fibers from the fourth, fifth and sixth cervical nerves
336 ABRAM T. KERR
4 times, 2.28 per cent of the cases; from the fifth and sixth 4 times, 2.28 per cent of the cases; from the fourth, fifth, sixth and seventh cervicals 98 times, 56 per cent of the cases; from the fifth, sixth and seventh 54 times, 30.85 per cent of the cases; from the fourth to the eighth cervical inclusive, 2 times, 1.14 per cent of the cases; from the fourth cervical to the first thoracic inclusive 6 times, 3.42 per cent of the cases; from the fifth cervical to the first thoracic 7 times, 4 per cent of the cases.
Herringham found the seventh entering the musculocutaneous in only 4 out of 39 cases, and in 28 examined to see if both the fifth and sixth entered he found the sixth absent in only one. Wichmann reports, from the literature, its origin from the fourth, fifth and sixth in 1 case, and from the fifth and seventh in another, from the fifth and sixth in 60 cases and from the fifth, sixth and seventh in 44 cases. Schumacher found the fifth and sixth entering 5 times, the fifth, sixth and seventh 4 times, and the fourth, fifth and sixth once.
If these 155 records are added to my 175 cases we have a total of 330 records of the musculocutaneous nerve. In 6 of these, or 1.82 per cent, it may receive fibers from the fourth, fifth and sixth cervical nerves. In 103, or 31.21 per cent, its fibers may come from the fifth and sixth. In 204, or 61.82 per cent, the seventh also sends fibers to the musculocutaneous, which in 98 of these, or 29.70 per cent is formed by the fourth, fifth, sixth and seventh, and in 106, or 32.12 per cent, by the fifth, sixth and seventh. In two its fibers come from the fourth to the eighth cervical nerves inclusive; in 6 or 1.82 per cent, from the fourth cervical to the first thoracic inclusive and in 7, or 2.12 per cent, from the fifth cervical to the first thoracic inclusive. In 1 instance it is formed from the fifth and seventh cervical nerves and in 1 from the fifth cervical alone. The seventh cervical nerve appears to take part in the formation of the musculocutaneous nerve in 220 instances, or more than two-thirds of the cases. In nearly a third of the cases, however, the seventh cervical sends no fibers to the musculocutaneous and it is not at all impossible that maceration with acid would show it to be absent more often.
BRACHIAL PLEXUS OF NERVES IN MAN 337
THE NERVE TO THE CORACOBRACHIALIS MUSCLE
In the above description of the musculocutaneous nerve no mention has been made of any of its branches of distribution. The nerve to the coracobrachiaHs muscle is usually described as a branch of the musculocutaneous nerve. In many cases, however, it takes origin from the brachial plexus independent of the musculocutaneous nerve and there may be more than one nerve to the muscle.
A record of the branches of the musculocutaneous nerve was not made for all of the plexuses of my series, so that I have but 109 records of the nerve to the coracobrachialis muscle.
In 54 plexuses, or 49.54 per cent of the 109 in which there are records, the nerve to the coracobrachialis muscle arises as a branch of the musculocutaneous nerve. There is but -a single branch arising from the musculocutaneous nerve for the muscle in 30 of these cases (fig. 2 and 15). In 2 of the above the musculocutaneous arises from the ventral division of the cephalic trunk. In the remaining 24 instances there is more than 1 branch. In 14 of these, there are two separate branches (fig. 25), in 6 of them there are 3 independent branches (figs. 3 and 14) ; and in 3 instances there are 4 branches. In one of these last three cases, the musculocutaneous nerve arises from the ventral branch of the cephalic trunk of the plexus, but one of its branches to the coracobrachialis muscle receives shortly after its origin a small branch from the ventral division of the seventh cervical nerve (fig. 18). In the remaining instance in which the nerve to the coracobrachialis arises from the musculocutaneous nerve, the nerve receives soon after its origin a small branch from the medial fasciculus of the plexus and in this case there is a second nerve to the muscle coming from a branch connecting the musculocutaneous with the median nerve.
In the remaining 55 plexuses at least one of the nerves to the coracobrachialis muscle arises from some other branch or division of the brachial plexus than the musculocutaneous nerve.
In 35 instances, or 32.11 per cent of the 109 plexuses, one of the branches to the coracobrachialis muscle arises from the lateral fasciculus of the plexus. In 19 of these, this is the only
338 ABRAM T. KERR
branch to the muscle (figs, 8, 10, 13). In another of the above 19 the nerve to the coracobrachiaUs muscle gives off a branch that rejoins the lateral fasciculus close to the point where the musculocutaneous nerve arises. In one of the above 19 the musculocutaneous arises from a trunk in common with the ulnar and median nerves and in another it is given off from the median in two separate branches.
In 3 instances there is a second branch from the lateral fasciculus to the coracobrachialis muscle. In 8 cases the second branch to the muscle arises from the musculocutaneous nerve (fig. 12), and in 5 others there are two additional branches both coming from the musculocutaneous nerve.
There is another plexus in which in addition to the nerve from the lateral fasciculus there is another nerve to the muscle arising from the seventh cervical nerve and another in which the second nerve comes from the lateral head of the ulnar nerve (fig. 24).
In 8 cases the nerve to the coracobrachialis muscle arises from the seventh cervical nerve. (These are in addition to the case mentioned above where there was a communicating branch from the seventh cervical to one of the four branches arising from the musculocutaneous nerve.) In 4 of these this is the only branch to the muscle, in 4 there is a second branch coming from the musculocutaneous nerve.
In 4 plexuses in which the musculocutaneous does not arise from the lateral fasciculus of the plexus but from the trunk formed by the lateral fasciculus and the medial head of the median, the nerve to the coracobrachialis also arises from this trunk (fig. 6). In one case one of the nerves to the muscle arises from the median, the other from the musculocutaneous which in this case also comes from the median. In 2 instances one nerve comes from the lateral head of the median and the other from the musculocutaneous (fig. 22). In 1 case there is but one branch and this comes from the lateral head of the median, in another the single branch to the muscle comes from the medial head of the median (fig. 4) .
My maceration experiments seem to indicate that in some instances where at least one of the nerves to the coracobrachialis
BRACHIAL PLEXUS OF NERVES IN MAN 339
muscle appears to arise from the lateral fasciculus of the plexus or from the musculocutaneous nerve, the fibers may be found to come from the seventh cervical nerve.
In my series of 109 records of the nerve to the musculocutaneous it was represented by a single nerve in 61, or 55.45 per cent of the 109 instances. The muscle is supplied by 2 nerves in 34, or 31.19 per cent; by 3 nerves in 11 cases, or 10.09 per cent; and by 4 nerves in only 3 instances or 2.57 per cent. It is probable that in some cases one or more of the nerves to the muscle may have been broken in the dissection or overlooked in the verification. It is altogether probable that in some cases at least there was an additional nerve that was not exposed since the foramen in the coracobrachialis muscle through which the musculocutaneous nerve passes was not opened up until late in the dissection and one of the branches to the muscle is often given off by the musculocutaneous nerve during its passage through the muscle.
The nerve to the coracobrachialis in my series arises in such a way that fibers of only the fifth and sixth nerves might enter it in two instances and in only 4 instances does it arise in such a way that the fibers of all the nerves but the seventh cervical can be excluded. In 61 instances its origin is such that the fibers of the fourth to the seventh cervical nerves inclusive might enter and in 31 cases fibers from the fifth to the seventh. In 11 plexuses fibers of the nerves caudal to the seventh cervical could not be excluded. In 6 of these the fourth to the eighth cervical and the first thoracic ; in 4, the fifth to the eighth cervical and the first thoracic ; and in 1 the fourth to the eighth cervical might have contributed.
Herringham found the nerve received its fibers from the seventh cervical nerve only, in all cases, except one in which there were fibers from the sixth cervical also.
THE SUPRASCAPULAR NERVE
The suprascapular nerve is usually described as arising from the cephalic trunk of the brachial plexus formed by the junction of the fifth and sixth cervical nerves.
340 ABRAM T. KERR
In my series there are 172 plexuses in which the records are satisfactory for the suprascapular nerve. In 108 or 62.79 per cent of these it arises from the cephalic trunk of the plexus. This trunk is formed by the union of the fourth, fifth and sixth cervical nerves in 69 (fig. 6), and by the fifth and sixth in 39 (fig. 8). In 12 instances the suprascapular nerve arises from the ventral branch of the cephalic trunk (fig. 12), and in only 1 of these the fourth cervical nerve fails to take part in the formation of this trunk. In 22 instances the nerve arises from the dorsal branch of the cephalic trunk and in 9 of these the fourth cervical does not enter into the fonxiation of the brachial plexus (figs. 3 and 7).
In many cases it is very difficult to tell whether the suprascapular nerve arises from the cephalic trunk or from the dorsal or ventral branch of it since it takes its origin just at the point where the trunk divides into dorsal and ventral branches (fig. 11). In all cases I have considered it as arising from the trunk unless it could be clearly shown that all of its fibers came from either the dorsal or the ventral branch of the trunk.
In 7 of the above 108 cases, the suprascapular nerve arises from a common stem which in 5 divides into suprascapular and subscapular nerves (fig. 5), and in one the stem divides into the suprascapular nerve and a branch which joins the subscapular nerve, while in the other case it arises from a similar common stem which divides into the suprascapular nerve and the dorsal scapular nerve to the rhomboid muscles.
All 7 of the above exceptional cases belong to group 1, types A and B of plexus. In 3 of the instances the branch arises from the cephalic trunk; in 2 from the ventral branch of this trunk; and in 2 from the dorsal branch of it.
In 13 of the 172 plexuses studied the suprascapular nerve arises from the trunk formed by the union of the fourth and fifth cervical nerves (fig. 13). In one other case it comes from the ventral branch of the above trunk and in another from the dorsal branch of the trunk. In 14 instances it arises from the fifth cervical nerve alone (fig. 2) . In one of these latter the fourth cervical nerve enters the plexus but the suprascapular arises high up in
BRACHIAL PLEXUS OF NERVES IN MAN 341
the plexus before the fourth nerve joins the fifth. In one other case the suprascapular arises from the ventral division of the fifth cervical nerve (fig. 15).
From the above it will be seen that in 30 plexuses out of 172 it can be surely determined that no nerve caudal to the fifth cervical enters the plexus. In 15 of these, the fourth nerve may contribute but in the remaining 15 plexuses the suprascapular comes exclusively from the fifth cervical nerve.
There are 142 cases from which the sixth cervical nerve can not be excluded from the suprascapular nerve. In 93 of them the suprascapular may receive fibers from the fourth cervical nerve (group 1 plexuses) and in 49 can receive no such fibers (groups 2 and 3 plexuses). It will be seen then that while the plexuses in which the suprascapular nerve receives no fibers from the sixth cervical nerve are almost equally distributed between those with and those without a branch from the fourth cervical nerve; that the plexuses in which the sixth cervical nerve, that is, a more caudal nerve, may contribute to the suprascapular nerve are nearly twice as many of them in the group with a branch from the fourth cervical as in the group without this nerve.
If the plexuses of group 1 are more cephalic in position we should expect to find fewer instances among them in which the suprascapular nerve receives fibers from the sixth cervical nerve than in the more caudally placed plexuses of groups 2 and 3, while the reverse appears to be the case. It must, of course, be remembered that some of the plexuses in which fibers from the sixth nerve could not, by dissection, be excluded from the suprascapular nerve would show, if macerated in nitric acid, that fibers from this nerve did not enter into the formation of the suprascapular.
Wichmann reports upon only 34 cases of suprascapular nerve from the literature, in 17 of these it arose from the fifth and sixth cervical and in 17 from the fifth cervical nerve alone. Schumacher gives the fifth cervical as the dominant spinal nerve supplying fibers to the suprascapular but he also notes in his table the presence of fibers from the sixth and occasionally from
342 ABRAM T. KERR
the fourth cervical nerve. He does not, however, give the number of cases of each that he found.
THE SUBCLAVIUS NERVE
The nerve to the subclavius muscle is usually described as arising from the cephalic trunk of the brachial plexus, occasionally from the fifth cervical nerve.
The nerve is a slender twig and is often broken in the dissection so that among the 175 plexuses of my series, it was satisfactorily dissected and recorded in only 83 cases.
In 18 or 21.68 per cent of these it arises from the fifth cervical nerve after the fourth has joined it so that the fibers of the fourth cannot be excluded. In 13 instances it is found as a single separate branch (fig. 11) ; in 3 it arises from a common stem with a branch to the phrenic nerve; and in 2 from a common stem with the dorsal scapular nerve to the rhomboid muscle.
In 22 plexuses or 26.50 per cent it arises from the fifth cervical nerve only; in 10 as a separate branch (fig. 16), and in 10 from a common stem with a branch to the phrenic nerve (fig. 25) ; and in 1 from a branch common to it and the dorsal scapular nerve. There is also one of the above instances in which it arises from a stem common to it and a branch to the phrenic nerve that arises from the fifth cervical nerve but receives a branch from the sixth before dividing (fig. 7).
In 41 or 49.39 per cent of the 83 cases it arises from the cephalic trunk or its ventral branch. In 27 of these this trunk is formed by the fourth, fifth and sixth cervical nerves. In 20 of these instances it comes from the main branch of the cephalic trunk; 14 times as a single branch (fig. 6), and 6 times in combination with a branch to the phrenic nerve. In 7 of the above 27 cases the subclavian nerve arises from the ventral branch of the cephalic trunk, in 5 as a single branch, in 1 in combination with a branch to the phrenic nerve and in 1 with the lateral anterior thoracic nerve.
Id 14 of the 41 instances, in which the nerve arises from the cephalic trunk, this trunk is formed by the fifth and sixth cervical nerves only. In 9 of these the nerve arises from the undivided
BRACHIAL PLEXUS OF NERVES IN MAN ' 343
cephalic trunk; in 6 instances singly (fig. 8) ; and in 3 in combination with a branch to the phrenic nerve. In 5 of the 14 instances it arises from the ventral brancli of the cephalic trunk, in 4 singly and in 1 with the lateral anterior thoracic nerve.
In 1 instance the nerve to the subclavius arises as a single branch from the sixth cervical nerve and in 1 instance it arises also as a single branch from the lateral cord of the plexus. The cord in this latter instance is formed from the ventral branches of the cephalic trunk, formed from the fourth, fifth and sixth cervical nerves, combined with the ventral branch of the seventh cervical nerve.
In 54 of the above plexuses or 65.06 per cent the subclavius nerve arises as a single branch. In 24 or 28.67 per cent it comes from a stem common to it and a branch to the phrenic, in 3 from a branch common to it and the dorsal scapular nerve, and in 2 from a stem from which one of the branches of the lateral anterior thoracic nerve also arises.
The records given by others of the spinal nerve or nerves from which the subclavius nerve arises are very incomplete, doubtless because the nerve is so delicate and so often broken in the dissection. Wichmann in his synopsis of the literature up to 1900 does not report clearly the number of cases recorded. He states that it has been found arising from the third cervical nerve by one author, from the fourth by one, and from the fifth by five authors. The nerve was reported as coming from the fifth and sixth cervical nerves by two authors; from the fifth, sixth and seventh by 1. The sixth cervical alone gave rise to the nerve in 2 instances reported by one author and the seventh and eighth by 1. He gives the fifth and sixth as the normal of Renz. Schumacher reports the fourth and fifth as found in Bolk's case. In his own investigations the fifth was the dominant nerve; the sixth sometimes entering. My results show that out of 83 satisfactory records the nerve to the subclavius may receive fibers from the fourth and fifth cervical nerve in 18 instances; from the fifth cervical only in 21 cases; from the fourt*h, fifth and sixth cervical nerves in 27 instances; from the fifth and sixth cervical nerve in 15; from the sixth cervical in 1 ; from the fourth,
344 ' ABRAM T. KERR
fifth, sixth, seventh in 1. It will be noted then that in 82 instances or in every plexus but one, the fifth cervical may send fibers to the subclavius; that the fourth cervical may enter in 47; the sixth in 44; and the seventh but once. In 39 instances the fibers may come from the fifth or fourth and fifth cervical nerves where the fourth enters the plexus, and in 42 cases the fibers may come from the fifth and sixth, or the fourth, fifth and sixth cervical nerves where the fourth enters the plexus.
THE CUTANEOUS NERVES TO THE MEDIAL SIDE OF THE ARM
The cutaneous nerves to the axillary fossa and its borders and the nerves to the skin of the medial side of the arm and the contiguous regions on the dorsomedial and ventromedial side of the arm are derived from several different sources. The nerves to the axillary region are mostly derived from the lateral cutaneous branches of the intercostal nerves, usually the second, and third, but at times the first and fourth contributing and also branches from the medial brachial cutaneous and the medial antibrachial cutaneous nerves or a separate nerve from the plexus arising independently. The medial side of the arm distal to the axilla and the adjoining dorsal and ventral regions is supplied mostly by the medial brachial cutaneous and intercostobrachial nerves. This latter coming usually from the second intercostal nerve occasionally from one of the others. There are also at times branches to this region of the arm derived from the medial antibrachial cutaneous nerve or an independent nerve that perhaps should be called a second medial brachial cutaneous. In addition, there are branches to the adjoining dorsal region derived from the axillary and radial nerves, with these latter I shall not deal now. It has been extremely difficult to get satisfactory student records of the distribution of the nerves of this region, even when the dissections were most excellent and the peripheral attachments of the nerves were not disturbed. The nerves here, however, were so frequently loosened that their exact distribution was difficult to verify. For the above reasons it was often difficult when there were several branches from the plexus to determine definitely how they should be named. In
BRACHIAL PLEXUS OF NERVES IN MAN .'M5
these cases the nerves were classified and named as carefully as possible at the time the record was verified but as the dissection of the plexus came much later than the working out of the peripheral distribution, the exact area supplied by each branch from the plexus could not always be determined.
THE MEDIAL BRACHIAL CUTANEOUS NERVE
The medial brachial cutaneous nerve (lesser internal cutaneous or nerve of Wrisberg) is usually described as rising from the medial trunk of the brachial plexus. My records are complete and satisfactory for 166 plexuses. In 137, or in 82.59 per cent, it is represented by a single branch and in 28 plexuses it is given off as two branches and in 1 as three separate filaments. In addition to this there are 9 cases in which there is recorded a branch given off by the medial antibrachial cutaneous nerve near its origin that anastomoses with the intercostobrachial. I am inclined now to classify all these as accessory medial brachial cutaneous nerves.
As this nerve and its branches are very small and as they are imbedded in a considerable mass of connective tissue it must be remembered that there is great danger of breaking or entirely overlooking and cutting away small accessory and communicating branches. This report is then positive for the branches and connections found and recorded, but it is not negative for those not recorded. There were undoubtedly other cases in which there was more than one nerve which supplied the region usually assigned to the medial brachial cutaneous nerve. There is much need of more very careful study of the interrelations of this nerve, the intercostobrachial, the posterior brachial cutaneous branch of the radial, and the cutaneous branches from the medial antibrachial cutaneous nerve which supply the medial and dorsal surfaces of the arm.
Of the 137 specimens in which the nerve arises as a single branch it comes directly and separately from the caudal trunk or medial fasciculus of the plexus in 92 (fig. 3) and from the dorsal division of the caudal trunk in 2 (fig. 7). In 11 other cases it arises separately, in 6 from the first thoracic nerve, in 4 from the ulnar
346 ABRAM T. KERR
nerve and in 1 by two roots, one from the eighth cervical and one from the first thoracic nerve.
In 32 instances the medial brachial cutaneous arises from a common branch from which the medial antibrachial cutaneous or the medial anterior thoracic or both of these arise (figs. 6, and 17). In 31 of these, this branch arises from the caudal trunk or the medial fasciculus of the plexus and in the other case from the first thoracic nerve.
In 29 cases there is more than one nerve that was classed as medial brachial cutaneous, in addition to the cases where a branch from the medial antibrachial cutaneous anastomoses with the intercostobrachial.
There are 36 of the 166 satisfactory plexuses in which a single medial brachial cutaneous nerve arises directly from the caudal trunk of the plexus (fig. 3). In 23 of these there is an anastomoses with the intercostobrachial. One of these sends a branch to the medial anterior thoracic nerve, another to the medial antibrachial cutaneous and a third to the radial, while two others receive branches from the medial antibrachial cutaneous nerve. In 13 cases there is no record of communication between the medial brachial cutaneous and the intercostobrachial. In two of these the medial brachial cutaneous receives a branch- from the medial antibrachial cutaneous and in 2 others there is an anastomosis between a branch of the medial antibrachial cutaneous and the intercostobrachial nerve.
There are 6 instances in which the medial brachial cutaneous nerve is single and arises from the caudal trunk of the plexus in combination with some other nerve. In 2 of these it is combined with the medial anterior thoracic nerve and in 1 of these it sends a branch to the medial antibrachial cutaneous which anastomoses with the intercostobrachial. In 3 cases it is combined with the medial antibrachial cutaneous, in 2 of these anastomosing with the intercostobrachial. In the last of the 6 cases it arises from a stem common to it and both of the above mentioned nerves and anastomoses with the intercostobrachial (fig. 27).
In 56 plexuses the single medial brachial cutaneous nerve arises directly from the medial fasciculus of the plexus. In 23 of these
BRACHIAL PLEXUS OF NERVES IN MAN ' 347
there is no anastomosis with the intercostobrachial (fig. 21). One of the 23 sends a branch to the medial antibrachial cutaneous and in 2 others there is an anastomosing branch from the medial antibrachial cutaneous to the intercostobrachial nerve. In the remaining 33 cases where the nerv.e arises directly it anastomoses with the intercostobrachial (fig. 18). In one of these it arises by 2 heads (fig. 8), in another it sends a branch to the posterior division of the caudal trunk. In 3 of the above, the medial antibrachial cutaneous also anastomoses with the intercostobrachial nerve.
There are 25 instances in which the medial brachial cutaneous nerve arises from the medial fasciculus of the plexus in combination with some other nerve. In 16 of these, it is in common with the medial antibrachial cutaneous (fig. 15) and in 8 of these it anastomoses with the intercostobrachial In 3 of the above 25 cases, the medial brachial cutaneous is combined with the medial anterior thoracic nerve (fig. 14). In 6 instances it arises from a branch common to it and the medial antibrachial cutaneous and the medial anterior thoracic nerve (fig. 17), and in 3 of these it anastomoses with the intercostobrachial nerve.
There are 2 instances in which the medial brachial cutaneous nerve arises directly from the dorsal division of the caudal trunk and in one of these it anastomoses with the intercostobrachial nerve (fig. 7).
There are 4 plexuses in which it arises singly from the ulnar nerve and in one of these it anastomoses with the intercostobrachial.
In 6 instances there is a single medial brachial cutaneous nerve arising directly from the first thoracic nerve and in 5 of these it anastomoses with the intercostobrachial. In one case it arises from the first thoracic by a common stem with the medial antibrachial cutaneous nerve and in another sends a branch to the dorsal division of the caudal trunk.
There are 29 cases in which there are 2 or more branches arising from the brachial plexus that were classed as medial brachial cutaneous nerves. This does not necessarily mean that there is a larger supply in these cases but that the branches arise from
348 " ABRAM T. KERR
the plexus separately instead of by a common stem. In 6 of the above both branches arise from the caudal trunk and in 5 of them one branch anastomoses with the intercostobrachial. In one of them, one branch receives a branch from the medial antibrachial cutaneous (fig. 10.) ; in another case a branch of one of the nerves joins the medial antibrachial cutaneous (fig. 5); and in a third plexus one branch communicates with the radial nerve. In one of these plexuses one of the branches arises in common with the medial anterior thoracic nerve. In 8 other cases where there are 2 branches, one of them arises from the caudal trunk and this branch anastomoses with the intercostobrachial nerve. It arises in common with the medial anterior thoracic in 2 instances. In 7 of the above the second branch arises from the medial fasciculus of the plexus and this does not anastomose in 5 but communicates with the intercostobrachial in 2 instances and also with the medial antibrachial cutaneous in one of them. Another of the above sends a branch to the posterior fasciculus of the plexus. In one of the above 7 cases the nerve arises from a stem common to it and the medial anterior thoracic (fig. 11); another from a stem in common with the medial antibrachial cutaneous nerve.
In 12 cases both of the branches arise from the medial fasciculus. In 7 of these they both arise directly from the medial fasciculus and in 4 neither branch anastomoses but in 2 one branch and in one both branches anastomose with the intercostobrachial nerve. Of the remaining 5 cases, in 4 one branch arises directly from the medial fasciculus and anastomoses with the intercostobrachial but the second branch arises from the medial fasciculus in common with the medial antibrachial cutaneous in one (fig. 20), with the medial anterior thoracic in one, with both of these nerves in one. In the fourth case both branches arise from the medial fasciculus of the plexus; one with the medial antibrachial cutaneous; one with the medial anterior thoracic. In the fifth instance, both branches arise from the medial fasciculus by a common stem with the medial antibrachial cutaneous.
In one instance one branch is from the medial fasciculus and
BRACHIAL PLEXUS OF NERVlIS IN MAN 349
the other comes from a small dorsal division of the caudal trunk that joins the posterior fasciculus. Both anastomose with the intercostobrachial. In one case both branches arise from the first thoracic nerve and one of them anastomoses with the intercostobrachial. There is one instance where there are 3 branches that were classified as medial brachial cutaneous nerves; these all arise from the medial fasciculus of the plexus from a stem from which the medial antibrachial cutaneous also arises. One or two of them might possibly be classified as branches of this latter nerve.
The medial brachial cutaneous nerve arises by itself from one of the main branches of the brachial plexus in 103 of the 137 plexuses where there was a single nerve.
In 20 instances the single medial brachial cutaneous arises from a stem common to it and the medial antibrachial cutaneous; in 5 from a stem common to it and the medial anterior thoracic ; and in 8 from a stem common to it and both of the above nerves. In the 29 cases where there are two or more nerves, there are 59 nerves recorded and 42 of these arise separately; 10 with the medial antibrachial cutaneous; 6 with the medial anterior thoracic ; and one with both of these nerves. It will be seen then that the medial brachial cutaneous arises from the plexus as an independent branch in 73.97 per cent of the cases.
The records show that the medial brachial cutaneous nerve anastomoses with the intercostobrachial in 101 instances or in 60.84 per cent of the cases. There is no doubt that there were many other plexuses in which such a connection existed but it was broken before the record could be verified.
The medial brachial cutaneous nerve arises from the caudal trunk of the brachial plexus or one of the divisions of this in 157 of the 166 plexuses. It therefore may receive fibers from the eighth cervical and first thoracic in all of these. In addition, there is one case where it arises from these nerves by separate roots. The eighth cervical and first thoracic nerves may send fibers to it in 95.18 per cent of the cases. In one of the type A plexuses it arises from the caudal trunk distal to the point where the branch from the seventh cervical joins this trunk so that in this case the seventh cervical cannot be excluded.
THE AMERICAN JOURNAL OF ANATOMY, VOL. 23, NO. 2
350 ■ ABRAM T. KERR
In Wichmann's tabulation, the eighth cervical and first thoracic are credited with sending fibers to the nerve in 9 cases, the first thoracic in 84 and the seventh cervical in 1.
THE MEDIAL ANTIBRACHIAL CUTANEOUS NERVE
The medial antibrachial cutaneous (internal cutaneous, ulnar antibrachial cutaneous) nerve is usually described as arising from the caudal trunk of the brachial plexus.
There are 174 satisfactory records in my series. There are 95 of these in which the nerve arises from the medial fasciculus of the plexus singly and with no anastomosis with the intercostobrachial. In 86 of these there are no anastomoses with any nerve (fig. 4) ; in 3 the nerve receives a branch from the medial anterior thoracic nerve; in one it receives a branch from the caudal trunk, a sort of second head; in 2 a branch from the medial brachial cutaneous joins it and in 4 it sends a branch to this nerve. There are 10 other plexuses in which the medial antibrachial cutaneous nerve arises from the medial fasciculus of the plexus but it anastomoses wdth the intercostobrachial in these, and in one of them it receives a branch from the medial brachial cutaneous nerve.
There are 36 cases in which the medial antibrachial cutaneous nerve arises from the medial fasciculus of the plexus from a stem common to it and some other nerve. In 19 cases it arises with the medial brachial cutaneous (fig. 6); in 8 with the medial anterior thoracic; and in 7 with both of these nerves (fig. 1). In 17 of these cases there is no anastomosis with the intercostobrachial but in the 2 other cases there is. In one of these it arises with the medial brachial cutaneous and sends a branch to the radial ; in the other, with the medial anterior thoracic and receives a branch from the medial brachial cutaneous.
The medial antibrachial cutaneous nerve arises from the caudal trunk of the plexus singly and without anastomosing with the intercostobrachial in 12 instances (fig. 2). In one of these there are 2 roots ; in one it received a branch from the medial brachial cutaneous; and in one it gives a branch to the radial nerve. There are 4 other cases in which the nerve arises from
BRACHIAL PLEXUS OF NERVES IN MAN 351
the caudal trunk of the plexus and has no anastomosis with the intercostobrachial. In 2 of these it arises in combination with the medial brachial cutaneous; in one with the medial anterior thoracic nerve; and in one with both of these (fig. 27).
There are 7 cases in which the medial antibrachial cutaneous nerve arises from the ulnar nerve and has no anastomosis with the intercostobrachial. In one of these it arises from a stem common to it and the medial anterior thoracic.
There are 4 instances where the nerve arises from the first thoracic without connection with the intercostobrachial. In one of these it arises in common with the medial brachial cutaneous nerve.
There are 6 plexuses in which 2 nerves were recorded as medial antibrachial cutaneous. In 2 these both arise from the medial fasciculus of the plexus, and in one of these one nerve anastomoses with the intercostobrachial and the other arises from a stem in common with the medial brachial cutaneous; in the third case, both nerves come from the caudal trunk ; in the fourth both come from the medial fasciculus, the first by a common stem with the medial brachial cutaneous and the second singly. In the fifth instance with two nerves, one arises from the medial fasciculus and the other a slender fascicle from the eighth cervical nerve. In the sixth instance one comes from the caudal trunk and one from the medial fasciculus of the plexus.
There are 143 or 82.18 per cent of the plexuses in which the medial antibrachial cutaneous nerve arises from the medial fasciculus of the plexus besides 3 in which there are 2 nerves. There are 16 plexuses in which the nerve arises from the caudal trunk besides 2 in which the nerve is double.
In all the plexuses except 4 in which the nerve arises from the first thoracic nerve only, we cannot exclude fibers of the eighth cervical as well as the first thoracic. There are 170 such cases or 97.70 per cent. In 3 of the 5 plexuses of type A that are included in the above, the seventh cervical nerve also cannot be excluded. The medial antibrachial cutaneous nerve may receive its fibers from the eighth cervical and first thoracic in 167 cases; from the seventh and eighth cervical and first thoracic
352 ABRAM T. KERR
in 3 ; and from the first thoracic in 4. It must always be remembered that the second thoracic is not considered in my records.
Wichmann reports from the hterature 51 cases in which the eighth cervical and first thoracic nerves entered the medial antibrachial cutaneous and 38 in which the first thoracic only enters the nerve. Schumacher found out of 10 cases that the eighth cervical and first thoracic enter the nerve in 8 and the first thoracic in 2. Adding the above to my records, w:e have the possibility of the medial antibrachial cutaneous nerve deriving its fibers from the eighth cervical and first thoracic in 226 cases; the first thoracic alone in 44 cases and the seventh and eighth cervical and first thoracic in 3.
In 25 instances the medial antibrachial cutaneous nerve arises from a common stem with the medial brachial cutaneous; in 9 with the medial anterior thoracic and in 9 with both of the above nerves. In 10 instances it has a connection with the intercostobrachial. In one of these the nerve is double and both branches communicate.
THE MEDIAL ANTERIOR THORACIC NERVE
The medial (internal) anterior thoracic nerve is usually described as arising from the caudal trunk of the brachial plexus.
In my series there are 151 satisfactory records for this nerve. In 105 of these, or 69.53 per cent, it arises from the medical fasciculus of the plexus (fig. 3) ; in 38, or 24.50 per cent, it arises from the caudal trunk of the plexus (fig. 2) ; in 3 from the eighth cervical nerve (fig. 4) ; in one from the medial head of the median nerve; and in one from the ulnar nerve; in 3 cases by two roots, one from the medial fasciculus and one from the seventh cervical nerve.
Of the 105 cases that arise from the medial fasciculus of the plexus, in 83 the nerve arises directly from the plexus, in one case by two roots. In 9 of the 83 the nerve gives off a branch and in one it receives a branch from the medial brachial cutaneous nerve. In 4 instances the branch given off goes to the skin of the arm, shoulder or axilla. In one it supplies an axillary slip of the latissimus dorsi muscle. In this case the seventh cervical nerve
BRACHIAL PLEXUS OF NERVES IN MAN 353
sends a branch to the caudal trunk, plexus type A, so that this nerve cannot be excluded from the medial anterior thoracic. In 3 cases it communicates with the medial^antibrachial cutaneous nerve and in one with the intercostobrachial.
In the other 22 instances where the nerve arises from the medial fasciculus of the plexus it comes off from a stem common to it and some other nerve, with the medial antibrachial cutaneous in 8 instances; with the medial brachial cutaneous m 6, and with both of these in 8 (fig. 1).
In 32 of the 38 instances in which the medial anterior thoracic nerve arises from the caudal trunk of the plexus, it is single and in 6 it is from a stem, with the medial brachial cutaneous in 5 (fig. 11), and with both the medial brachial cutaneous and medial antibrachial cutaneous in one (fig. 27).
The eighth cervical and first thoracic nerves could neither of them be excluded from the medial anterior thoracic nerve in 144 of the 151 satisfactory records, or 95.36 per cent. The seventh and eighth cervical and first thoracic nerves may send fibers in 4 cases, while the nerve receives fibers only from the eighth in 3 instances.
Herringham reports the medial anterior thoracic nerve as receiving its fibers from the eighth cervical and first thoracic nerves in 8 out of 10 cases. In the other two the eighth cervical alone sent fibers to it. I found only 3 cases out of 151 in which the first thoracic nerve failed to enter the plexus. It is possible that some others if macerated would show that both nerves did not enter into its formation, but this could not be proven by dissection. In 3 cases the seventh cervical nerve positively entered the nerve and in the plexus of type A it may have entered.
THE LATERAL ANTERIOR THORACIC NERVE
The lateral (external) anterior thoracic nerve is usually described as arising from the cephalic trunk of the plexus.
In my series there are 166 satisfactory cases. The nerve arises by a single root in 39 instances, or in 23.49 per cent of the cases; by two roots in 91, or 54.81 per cent; by three roots in 33, or in 19.87 per cent; and by four roots in 3.
354 ABRAM T. KERR
Of the' 39 plexuses in which it arises by a single root, this comes from the cephalic trunk of the plexus in 2 (fig. 2), from the ventral division of the cephalic trunk in 12 (fig. 4), from the lateral fasciculus in 17 (fig. 21), from the seventh cervical nerve in 2, and from the ventral division of the seventh cervical nerve in 6. One of the nerves that arises from the lateral fasciculus sends a branch to the medial head of the median nerve.
In 73, or 78.02 per cent, of the 91 cases where the nerve arises by two roots, one of these comes from the ventral division of the cephalic trunk of the plexus and the second comes from the ventral division of the seventh cervical nerve (fig. 3). In 7 cases both roots arise from the lateral fasciculus of the plexus (fig. 20). One comes from the ventral division of the cephalic trunk and one from the lateral fasciculus in 3 (fig. 11) ; one from the ventral division of the sixth and one from the ventral division of the seventh cervical nerve in 2. There is one instance of each of the following: one branch from the ventral and one from the dorsal division of the cephalic trunk, one from the lateral fasciculus of the plexus and one from the seventh cervical nerve, both from the seventh cervical, one from the seventh and one from the dorsal division of the sixth cervical, one from the lateral fasciculus of the plexus and one from the lateral head of the ulnar, one from the lateral fasciculus and one from the combined cephalic and intermediate trunks.
In 18, or 54.54 per cent, of the 33 plexuses where there are three roots to the lateral anterior thoracic nerve, one of these arises from the ventral division of the cephalic trunk and the other two from the ventral division of the intermediate trunk (seventh cervical nerve) (fig. 1). In 5 cases one root comes from the ventral division of the cephalic trunk, one from the lateral fasciculus of the plexus and one from the seventh cervical nerve. In 4 cases two roots come from the ventral division of the cephalic trunk and one from the seventh cervical nerve, or its ventral division. In 2 cases all three roots come from the lateral fasciculus of the plexus. Each of the following arrangements is found in one plexus only : one root from the ventral division of the fifth, one from the ventral division of the sixth and one from the ventral
BRACHIAL PLEXUS OF NERVES IN MAN 355
division of the seventh cervical nerves; one root from the fifth, one from the ventral division of the cephalic trunk and one from the ventral division of the seventh cervical nerve; one root from the ventral division of the cephalic trunk, one from the ventral division of the seventh and one from a ventral branch from the eighth cervical that goes to the lateral fasciculus (fig. 27); one root from the lateral fasciculus of the plexus and two from the ventral division of the seventh cervical nerve.
The three plexuses in which there are four roots have the same arrangement, one root comes from the ventral division of the cephalic trunk, one from the lateral fasciculus and two roots from the ventral division of the seventh cervical nerve. In one of these the root that comes from the cephalic trunk gives off a branch to the phrenic nerve.
In the total of 166 records there are only 15 cases in which the seventh cervical nerve may not contribute to the lateral anterior thoracic nerve and as 14 of these are in the group where there is but a single root to the nerve it makes one suspicious that in spite of all our care a second root may have been broken or overlooked. These 15 cases are nearly equally distributed between the group 1 and group 2 of plexuses, 8 of group 1 and 7 of group 2. There are 87 cases, or 52.40 per cent, in which the fourth, fifth, sixth and seventh cervical nerves may send fibers to the lateral anterior thoracic, and 51, or 30.72 per cent, in which the fifth, sixth and seventh may contribute. There is one plexus in which the fourth, fifth, sixth, seventh and eighth cervical nerves can none of them be excluded. This is the only instance in which fibers may come from the eighth. The sixth and seventh are the only contributing nerves in 3 instances and the seventh alone in 9.
Herringham believed that the seventh cervical nerve always contributes to the lateral anterior thoracic. He reports on 13 dissections that the fifth and sixth cervical nerves' also contribute to it in 5 instances and the sixth only in 8 cases. I can be sure that the fifth cervical does not enter the nerve in only 12 cases out of 166.
356 ABRAM T. KERR
THE RADIAL NERVE
The radial nerve (musculo-spiral) is usually described as one of the two terminal branches of the posterior fasciculus of the brachial plexus produced by the division of the fasciculus into radial and axillary.
In my series the radial nerve is formed by the division of the posterior fasciculus of the plexus in 138 plexuses, or 79.76 per cent of the 173 satisfactory records for this nerve (figs. 1 to 5).
There are, as already noted in connection with the dorsal fasciculus, 36 plexuses in which there is no true dorsal trunk but the radial and axillary nerves are formed by the union of dorsal branches of the plexus. There are 35 of these cases where the record for the radial nerve is satisfactory and in these cases the radial nerve is formed by the union of two heads.
In 19 of these a cord formed by the union of the dorsal divisions of the cephalic and intermediate trunks, after giving off the axillary nerve forms the cephalic head of the radial nerve. This joins the caudal head of the radial which is the whole of the dorsal division of the caudal trunk (fig. 6). The dorsal division of the intermediate trunk in two of these and the caudal head of the radial nerve in another sends a branch to the axillary nerve. In one of these the dorsal division of the caudal trunk is represented by two branches, one from the eighth cervical and one from the first thoracic i^erve. In another the dorsal division of the caudal trunk comes from the eighth cervical only. More than the usual amount of connective tissue had been removed in this case so that three of the branches for the muscles of the arm that ordinarily arise from the radial came from its heads, two from the caudal head and one from the cephalic head. In two of the above 19 cases the radial nerve receives a branch from the medial fasciculus of the plexus, in one as a separate branch and in the other as a branch of the medial brachial cutaneous nerve that comes from the medial fasciculus. In 4 of the above instances, the radial gives off the thoracodorsal nerve.
In 10 cases the dorsal division of the cephalic trunk, after giving off the axillary nerve forms the cephalic head of the radial nerve. In two of these the dorsal division of the cephalic trunk
BRACHIAL PLEXUS OF NERVES IN MAN 357
is formed by the union of the dorsal divisions of the fifth and sixth cervical nerves (fig. 15). In the above 10 instances the caudal head of the radial nerve is formed by the union of the dorsal divisions of the intermediate and caudal trunks (fig. 7). In one of these the dorsal division of the caudal trunk is from the eighth cervical nerve only, but in this case the radial nerve receives a branch from the medial fasciculus and it also gives off the thoracodorsal nerve.
In another case the cephaHc head of the radial nerve is formed as above but the caudal head is formed by the dorsal division of the intermediate trunk being joined by the dorsal division of the eighth cervical nerve and more distad by the dorsal division of the first thoracic nerve.
In 4 cases the cephalic head of the radial nerve is formed by the dorsal division of the cephalic trunk after giving off the axillary nerve joining the dorsal division of the intermediate trunk. The caudal head of the radial nerve in these cases is formed by the dorsal division of the caudal trunk.
In one instance the cephalic head of the radial nerve is formed by the dorsal division of the cephalic trunk joining the dorsal division of the intermediate trunk after this has given off the axillary nerve. The caudal head of the radial is the dorsal division of the caudal trunk.
In 169, or 97.68 per cent of the cases, none of the nerves of the plexus can be excluded from sending fibers to the radial. In 109, the fourth, fifth, sixth, seventh and eighth cervical and first thoracic might contribute and in 60 the fourth cervical did not enter the plexus. In 4 instances, there was no dorsal branch from the first thoracic nerve so that in these this could be positively excluded.
Wichmann reports from the literature that fibers from the fifth, sixth, seventh and eighth unite to form the radial nerve in 98 cases; from the sixth, seventh and eighth in 27 cases; from the fifth, sixth, seventh and eighth cervical and first thoracic in 25 cases; the sixth, seventh and eighth cervical and first thoracic in 3; and the fifth, sixth and seventh; the sixth and seventh; and the seventh and eighth in one case each.
358 ■ ABRAM T. KERR
Schumacher found the fifth, sixth, seventh, eighth cervical and first thoracic 7 times and the fifth, sixth, seventh and eighth cervical nerves 3 times out of 10 cases.
In comparing my findings with those given above, I can only refer again to what I said concerning the first thoracic nerve when discussing the posterior fasciculus of the plexus.
THE AXILLARY NERVE
The axillary nerve (circumflex) is usually described as one of the terminal branches of the posterior fasciculus of the brachial plexus.
As noted in connection with the radial nerve, this is the condition found in 138 of the 173 satisfactory records in my series, or in 79.76 per cent. In 67 of these, or 38.72 per cent, the axillary is a single nerve (fig. 2) ; in 57, or 32.94 per cent, it gives off the axillary subscapular nerve to the teres major and axillary border of the subscapularis muscles (fig. 1) ; in 6 it gives off both the axillary subscapular nerves and the thoracodorsal nerve (fig. 6); in 4 it gives off the axillary subscapular and another separate branch to the axillary border of the subscapularis muscle (fig. 3); in another the axillary subscapular nerve and two additional branches to the subscapularis muscle; in 2 others both the axillary subscapular and thoracodorsal and a branch to the subscapularis muscle; and in another it gives off a branch to the axillary subscapular nerve.
In 35 of the 36 plexuses where there is no posterior fasciculus, the record for the axillary is satisfactory. In 16 of these it arises from a cord formed by the union of the dorsal branches of the cephalic and intermediate trunks (fig. 6). In 6 of these it is single, in 9 it gives off the axillary subscapular nerve, and in one both the axillary subscapular and the thoracodorsal nerve.
In 16 other cases of this group it arises from the dorsal division of the cephalic trunk (fig. 7). In 3 of these the dorsal division of the cephahc trunk is formed by the union of the dorsal divisions of the fifth and sixth cervical nerves. In 7 of these it is single, and in 8 it gives off the axillary subscapular nerve. In one of these it receives a small branch from the axillary subscapular nerve.
BRACHIAL PLEXUS OF NERVES IN MAN 359
In 2 other cases the axillary nerve arises from the dorsal division of the cephalic trunk and receives a branch. This comes from the trunk formed by the union of the dorsal branches of the intermediate and caudal trunks in one case and from the dorsal division of the intermediate trunk in the other case and gives off the thoracodorsal nerve before joining the axillary.
In the other one of the 35 cases, the axillary nerve arises from the dorsal division of the intermediate trunk.
The axillary nerve gives off no other nerves in 80 cases, or 46.24 per cent. The axillary subscapular nerve arises from it in 89 or 55.44 per cent.
It will be noted that in nearly 80 per cent of the above cases the nerve arises from the dorsal fasciculus of the plexus and in these cases it is not possible to tell whether or not all of the cervical nerves that go to the dorsal fasciculus send branches to the axillary nerve. From my maceration experiments I do not believe that as a rule they do. At the same time I cannot now exclude any.
The axillary nerve may receive fibers from any of the nerves from the fourth cervical to the first thoracic inclusive, in 92 instances, 53.17 per cent; from the fifth cervical to the first thoracic in 44 cases, 25.43 per cent; from the fourth to the eighth cervical in one case; from the fifth to the eighth cervical in 2 cases; from the fourth to the seventh cervical in 10; from the fifth to the seventh cervical in 6; from the fourth to the sixth cervical in 6 ; and from the fifth and sixth cervical nerves in 9 cases.
Wichmann has collected from the literature 142 cases. In 112 of these the fifth and sixth cervical nerves only entered the plexus; in 21 the fifth, sixth and seventh; in 7 the fifth, sixth, seventh and eighth cervical and first thoracic; and in 6 cases the fifth only. Schumacher in his 10 cases found the fifth and sixth cervical 7 times and the fifth, sixth and seventh 3 times. From my experience so far with macerated plexuses I am inclined to believe that the eighth cervical and first thoracic will be found sending fibers to the nerve seldom if at all. In what proportion the seventh will be found, I am unable to say from my maceration experiments. It appears to be present somewhat more often than previously reported.
360 ABRAM T. KERR
THE SUBSCAPULAR GROUP OF NERVES
In this group are included the nerves to the subscapularis, the teres major and the latissimus dorsi muscles. There has been some confusion in regard to the names. The nerve or nerves that supply the cephalic and middle parts of the subscapularis muscle was formerly designated as the upper subscapular nerve or nerves. To this group I shall apply the name subscapular nerve, 1, 2 or 3, according to the number found. The nerve that supplies the teres major muscle and the axillary border of the subscapularis muscle and that was formerly called the lower subscapular nerve I shall call the axillary subscapular nerve. The nerve that supplies the latissimus dorsi muscle and that was formerly known as the middle or long subscapular nerve, I shall follow the B. N. A. in calling the thoracodorsal nerve. In some cases the branch or branches that the axillary subscapular usually supplies to the axillary border of the subscapularis muscle are given off separately. I have designated these as the subscapular branches of the axillary subscapular nerve.
THE SUBSCAPULAR NERVES
The subscapular nerve (upper subscapular) is usually described as arising from the dorsal division of the cephalic trunk and as being often double.
In my series there are 157 satisfactory records of this nerve. In 84, or 53.50 per cent of them, there is a single nerve (fig. 4), in 64, or 40.76 per cent, there are two nerves and in 9, or 5.73 per cent, there are 3 nerves.
In 40 of the plexuses in which the subscapular is represented by a single branch, this arises from the dorsal division of the cephalic trunk of the plexus (fig. 8). In 2 of these there is another nerve to the subscapularis muscle arising from the axillary nerve, which both from its origin and relations I have considered as one of the branches that the axillary subscapular nerve sends to the subscapular muscle and which in this case arises separately. One of the 40 single nerves arises by two roots and another comes from the suprascapular nerve.
BRACHIAL PLEXUS OF NERVES IN MAN 361
In 17 plexuses where the nerve is single it arises from the cord formed by the union of the dorsal divisions of the cephalic and intermediate trunks (fig. 11).
In 13 instances the single nerve arises from the posterior fasciculus of the plexus (fig. 21). In 2 of these there is an additional branch that I regard as belonging to the axillary subscapular nerve.
In 7 cases the nerve arises from the dorsal division of the intermediate trunk (seventh cervical nerve) and in one case from the ventral division of this.
In one plexus the subscapular nerve comes ftom the fifth cervical nerve; in one by two roots, one from the cephalic trunk and the other from the dorsal" division of this ; in another, by three roots, one from the cephalic trunk with the suprascapular nerve, one from the lateral fasciculus of the plexus, and one from the intermediate trunk. In one plexus, the nerve comes from the dorsal division of the cord formed by the union of the cephalic and intermediate trunks and in one it comes from a cord formed by the union of the intermediate and caudal trunks. In one instance the nerve arises from the radial nerve. In this case the axillary subscapular and the thoracodorsal nerves also arise from the radial nerve.
In 7 of the plexuses where there is a single nerve this divides almost immediately after its origin into 2 branches in 5 cases and 3 branches in 2. The nerve frequently breaks up into several branches before entering the muscle but my records do not show the method of branching.
In 21 of the 64 instances where there are two subscapular nerves both arise from the dorsal division of the cephalic trunk (fig. 2). In two of these there is another separate nerve to the subscapularis muscle that comes from the axillary nerve and which I have considered as a part of the axillary subscapular nerve.
In 13 cases, one of the two subscapular nerves comes from the dorsal division of the cephalic trunk and the second from the posterior fasciculus of the plexus (fig. 1).
In 7 cases both branches come from the cord formed by the
362 • ABRAM T. KERR
union of the dorsal divisions of the cephaHc and intermediate trunks.
In 6 plexuses one branch comes from the cord just mentioned and the second from the dorsal division of the cephalic trunk. In one of these one of the branches from the dorsal division of the cephalic trunk arises with or from the suprascapular nerve.
In 9 instances both nerves come from the posterior fasciculus (fig. 20). In one of these there is another subscapular nerve coming from the axillary but classified as a part of the axillary subscapular nerve.
In 4 cases one nerve comes from the cord formed by the union of the dorsal divisions of the cephalic and intermediate trunks and the other from the posterior fasciculus (fig. 19).
There are 2 cases in which one branch comes from the fifth cervical nerve and the other from the dorsal division of the cephalic trunk. This second branch sends a small filament to join a cord from which the axillary subscapular and the thoracodorsal nerves arise. In one case one branch comes from the ventral and one from the dorsal division of the cephalic trunk and in one instance one comes from the cephalic trunk and one from the posterior fasciculus.
There are 9 plexuses in which there are three branches. In 5 of these two of the branches arise from the dorsal division of the cephalic trunk. The third branch in one of these comes from the dorsal division of the fifth cervical nerve ; in one it comes from the dorsal division of the cephalic trunk like the other two branches but has a second root from the dorsal division of the intermediate trunk in common with the thoracodorsal nerve (fig. 10) ; in one, the third branch comes from the trunk formed by the union of the dorsal divisions of the cephalic and intermediate trunks; in another from the posterior fasciculus; and in the last of this group from the axillary nerve. In one plexus one branch arises from the dorsal division of the intermediate trunk and two come from the posterior fasciculus of the plexus. In one case one branch comes from the cord formed by the union of the cephalic and intermediate trunks, one from the dorsal division of this, and a third from the posterior fasciculus. In one
BRACHIAL PLEXUS OF NERVES IN MAN 363
plexus all three branches come from the cord formed by the union of the dorsal divisions of the cephalic and intermediate trunks and in another one branch from this same cord and the other two from the posterior fasciculus of the plexus. In the first of these two last mentioned cases, there are two and in the second case there is one additional nerve to the subscapularis muscle but these are grouped with the axillary subscapular nerve.
From the above it will be seen that one subscapular nerve arises from the dorsal division of the cephalic trunk in 89 cases, or 56.68 per cent of the cases; from the cord formed by the union of the dorsal divisions of the cephalic and intermediate trunks in 30 or in 19.10 per cent; from the posterior fasciculus in 44 or in 28.02 per cent; and from various other divisions of the plexus in the other cases.
The subscapular nerve arises from the fifth cervical nerve in one case and from the seventh in 8 instances. In all the other cases it arises in such a way that two or more nerves may contribute fibers to it. In 40 cases the fourth, fifth and sixth may contribute and in 28 the fifth and sixth. In 22 instances the fourth fifth, sixth and seventh may send fibers and in 15 the fifth, sixth and seventh. In 34 plexuses all of the nerves from the fourth cervical to the first thoracic and in 9 from the fifth cervical to the first thoracic may contribute. Herringham ('87) reports on 41 cases and states that in the majority of cases the fifth nerve only sends fibers to the subscapular, but that often the sixth contributes but in no instance the seventh and eighth cervical. I found 8 plexuses in which the seventh cervical was the only nerve that could send fibers to it.
THE AXILLARY SUBSCAPULAR NERVE
The axillary subscapular nerve (lower subscapular) is usually described as arising from the posterior fasciculus of the plexus or one of the roots of this. It supplies the teres major muscle and the axillary border of the subscapularis muscle.
Among the 157 satisfactory records of the axillary subscapular nerves in my series, the nerve arises directly from the posterior fasciculus in 48 cases (fig. 2). In gne of these it receives a branch
364 ABRAM T. KERR
from the subscapular nerve and gives off a small branch to the latissimus dorsi muscle. In 5, it is formed from a common trunk with the thoracodorsal nerve. In 68 other cases it arises from the axillary nerve which takes origin from the posterior fasciculus (fig. 1), and in one from the radial nerve that arises from the posterior fasciculus. Its origin is directly or indirectly from the posterior fasciculus in 117 cases, or in 74.52 per cent of the cases.
It arises directly from the cord formed by the union of the dorsal divisions of the cephalic and intermediate trunks in 12 cases (fig. 13), and from the axillary nerve that takes origin from this cord in 9 others (fig. 6), making a total of 21 or in 13.37 per cent of the 157 cases.
It comes from the dorsal division of the cephalic trunk in 3 cases directly (fig. 10), and in 7 others from the axillary nerve that takes origin from the dorsal division of the cephalic trunk (fig. 23), making 10 in all.
In one other case it arises from the axillary nerve and this nerve arises by two roots, one from the dorsal division of the cephalic trunk and one from the dorsal division of the intermediate trunk.
In one plexus it arises from the dorsal division of the intermediate trunk and in 2 from the cord formed by the union of the dorsal divisions of the caudal and intermediate trunks.
In 5 instances it arises by two heads. In 4 of these one comes from the dorsal division of the cephalic, and one from the dorsal division of the intermediate trunk (fig. 7). In one of these the thoracodorsal nerve arises in common with the axillary subscapular nerve. In the fifth case, one root comes from the cord formed by the union of the dorsal branches of the cephalic and intermediate trunks and the other from the dorsal division of the caudal trunk. Immediately after its origin, the nerve receives a branch from the thoracodorsal nerve.
It will be noted then that the axillary subscapular nerve arises directly from one of the dorsal divisions of the brachial plexus in 71 instances or 45.22 per cent, and from the axillary nerve in 85 instances or 54.14 per c^nt.
BRACHIAL PLEXUS OF NERVES IN MAN 365
From those cases in which my records show the branches of the axillary subscapular nerve to the subscapularis muscle, it will be seen that in 21 instances there is a single branch; in 15 there are 2 branches, besides 3 cases in which there is one branch from the axillary subscapular nerve and a second branch from the axillary nerve close to it, and one case in which there are two branches from the axillary nerve to the subscapularis muscle, and none from the axillary subscapular nerve.
There are 5 cases in which there are three nerves to the axillary part of the subscapularis muscle. In 2 of these all three came from the axillary subscapular, in 2 cases two come from the axillary subscapular, and the third from the posterior fasciculus, and in the fifth case two branches come from the axillary subscapular and the third from the axillary nerve close to it.
In one plexus there are four branches from the axillary subscapular nerve to the axillary part of the subscapularis muscle.
There are 115 plexuses in which I cannot be sure that fibers from all the nerves of the plexus may not enter the axillary subscapular nerve. In 79 of these the nerves from the fourth cervical to the first thoracic may send fibers and in 36 from the fifth cervical to the first thoracic. In one case fibers may come from the fourth to the eighth cervical and in two from the fifth to the eighth; in 14 from the fourth to the seventh cervical and in 12 from the fifth to the seventh. In 6 cases the fourth, fifth and sixth cervical are the only nerves and in 4 the fifth and sixth. In one the seventh cervical and in 2 the seventh and eighth cervical and first thoracic may contribute.
Herringham was able to exclude the eighth cervical and first thoracic nerves from the axillary subscapular in all of his 41 cases. He found it arising from the fifth, sixth and seventh cervical nerves in 3 cases; the sixth and seventh in 9. The seventh nerve contributing to the plexus only in these 12 cases. The nerve arises from the fifth and sixth cervical nerves in 9 cases and from a trunk formed by branches of these nerves in 13 cases or 22 in all where the fifth and sixth may have formed the nerve. The sixth alone in 4 and the fifth alone in 3 cases formed this nerve.
THE AMERICAN JOURNAL OF ANATOMY, VOL. 23, NO. 2
366 ABRAM T. KERR
THE THORACODORSAL NERVE
The thoracodorsal (middle or long subscapular) nerve is usually described as arising from the posterior fasciculus of the plexus.
In my series of 161 satisfactory records for this nerve it arises singly from the posterior fasciculus in 93 instances or 57.76 per cent (fig. 2). In 2 of these the posterior fasciculus receives no fibers from the first thoracic nerve. In 4 of the above, in addition to its origin from the posterior fasciculus, the nerve has a second root, coming from the dorsal division of the caudal trunk in 2, from the dorsal division of the intermediate trunk in one, and from the posterior fasciculus itself in one.
In 7 cases the nerve arises from thie posterior fasciculus by a stem common to it and the axillary subscapular nerve. In 9 plexuses the nerve arises from the radial nerve which in 5 of these is one of the terminal divisions of the posterior fasciculus and in 3 others the radial nerve is formed by a branch from the trunk produced by the union of the dorsal divisions of the cephalic and intermediate trunks after giving off the axillary nerve joining the dorsal division of the caudal trunk. In another case the radial nerve from which the thoracodorsal arises is formed by a branch from the dorsal division of the cephalic trunk, after giving off the axillary nerve, joining the cord formed by the union of the dorsal division of the intermediate trunk and a dorsal branch of the eighth cervical and joined by a branch from the caudal trunk (fig. 28).
In 9 plexuses the nerve arises from the axillary nerve. In 8 of these this is one of the terminal divisions of the posterior fasciculus (fig. 17). In the other case the axillary nerve comes from the trunk formed by the union of the dorsal branches of the cephalic and intermediate trunks but the thoracodorsal nerve receives almost immediately after its origin from the axillary a branch from the dorsal division of the caudal trunk.
The thoracodorsal nerve arises either directly or indirectly from the posterior fasciculus of the plexus in 113 plexuses, or in 70.19 per cent.
In 18 instances the thoracodorsal nerve arises from the cord formed by the union of the dorsal divisions of the cephalic and
BRACHIAL PLEXUS OF NERVES IN MAN 367
intermediate trunks. In 3 of these it comes from a stem common to it and the axillary subscapular nerve. In one other case it gives off a small branch to supply the teres major muscle which is also supplied by the axillary subscapular.
In 10 plexuses the nerve comes from the dorsal division of the intermediate trunk, that is the seventh cervical nerve (fig. 15). In one of these it does not arise directly but comes from a branch that forms one of the heads of the axillary nerve.
The nerve arises in 4 cases by two roots, one from the dorsal division of the cephalic trunk and one from the dorsal division of the intermediate trunk (fig. 18). In one of these the stem formed by the union of the two roots gives origin also to the subscapular nerve and in another case to the axillary subscapular.
In 3 cases it arises from the dorsal division of the cephalic trunk. One of these gives off a branch that joins the axillary subscapular nerve.
The thoracodorsal nerve arises from the cord formed by the union of the dorsal divisions of the intermediate and caudal trunks in 6 instances (fig. 7), and in another it arises by two roots, one from the dorsal division of the intermediate trunk and one from the dorsal division of the caudal trunk. In one case the nerve arises from the dorsal division of the caudal trunk.
In 115 cases, or 71.42 per cent of this series, no nerve that enters the plexus can be excluded from sending fibers to the thoracodorsal nerve. In 73, the spinal nerves from the fourth cervical to the first thoracic inclusive enter the plexus and in 35 from the fifth cervical to the first thoracic. In one case all of the nerves from the fourth cervical to the eighth cervical and in 2 others from the fifth to the eighth.
In 14 cases the nerves from the fourth to the seventh cervical may contribute, in 8 from the fifth cervical to the seventh. In 3 instances the fifth and sixth cervical nerves; in 10 the seventh cervical; in 7 the seventh and eighth cervical and first thoracic; in one the eighth cervical and first thoracic are the nerves that may send fibers to the thoracodorsal nerve.
Herringham, from his study of 42 plexuses, found that the seventh cervical alone sent fibers to the thoracodorsal nerve in
368 ABEAM T. KERR
21 cases; the seventh and eighth in 13; sixth, seventh and eighth in one; the sixth, and seventh in 3; the fifth, sixth and seventh in 3 and the fifth, and sixth in one case. It will be noted that from only one case in his series was the seventh lacking. In my series there are 4 cases in which the seventh cervical nerve does not enter the thoracodorsal nerve. In 3 of these it comes from the fifth and sixth cervical nerve as in Herringham's case and in the other case from the eighth cervical and first thoracic nerves.
SUMMARY
1. The 175 brachial plexuses studied can be divided into three groups according to the nerves joining the cephalic border of the plexus.
2. Those plexuses that receive a branch from the fourth cervical nerve are grouped together as group 1. Over 62 per cent of the plexuses are formed in this way (fig. 1).
3. Those plexuses that receive no branch from the fourth cervical nerve but in which the whole of the ventral division of the fifth cervical nerve joins the plexus form a second group. Nearly 30 per cent of those studied are in this group (fig. 2).
4. Plexuses that receive no branch from the fourth cervical and in which a part of the fifth cervical nerve helps to form the cervical plexus form a third group that contains a little over 7 per cent of the plexuses (fig. 3).
5. The plexuses studied do not show that sex, color or side of the body have much if any influence upon the classification into these groups.
6. Plexuses that receive a branch from the fourth cervical nerve are more cephalic as regards the spinal column and those in which only part of the fifth enters the plexus are more caudal. The larger the branch from the fourth nerve to the brachial plexus the more cephalic the plexus and conversely, the larger the branch from the fifth to the cervical plexus, the more caudal the plexus.
7. The relative size of the nerves, especially those in the center of the plexus, is found to have but little value in estimating the position of the plexus as cephalic or caudal. This is because
BEACHIAL PLEXUS OF NERVES IN MAN 369
the diameter is dependent upon so many other factors than the nerve fibers.
8. Maceration shows how very complexly the nerve bundles interlace and join and how difficult it is, even when the epineurium is removed by maceration, to trace the bundles.
9. By anatomical methods the fibers of a given spinal nerve can rarely be traced through the plexus to their ultimate distribution. In only a few of the branches of the plexus can it be determined anatomically which spinal nerves send fibers to them.
10. The nerves cephalic to the seventh cervical join to form a cephalic trunk which then divides into dorsal and ventral branches in nearly 90 per cent of the cases.
11. The nerves caudal to the seventh unite to form a caudal trunk in over 95 per cent of the plexuses.
12. The seventh cervical remains single and forms the intermediate trunk in all cases.
13. In over 80 per cent of the cases the lateral fasciculus is formed by the union of the ventral branches of the cephalic and intermediate trunks.
14. The medial fasciculus is composed of the ventral branch of the caudal trunk in over 95 per cent of the plexuses.
15. In nearly 70 per cent of the plexuses the posterior fasciculus is formed by the union of the dorsal divisions of the cephalic, intermediate and caudal trunks. In over 20 per cent of the plexuses there is no true posterior fasciculus formed.
16. The plexuses are subdivided into seven subgroups or types based upon the nerves entering the medial or the lateral fasciculus.
17. In type A, group 1, the fourth cervical nerve sends a branch to the plexus and the seventh cervical nerve gives a branch to the medial fasciculus. There are less than 3 per cent of the plexuses of this type (fig. 4) .
18. In type B, group 1, the fourth cervical nerve sends a branch to the plexus and the medial fasciculus receives no branch from the seventh cervical nerve. Over 57 per cent of the plexuses are of this type (fig. 1).
19. Type C, group 1, differs from the preceding in having a branch from the caudal trunk or eighth cervical nerve to the
370 ABRAM T. KERR
lateral fasciculus or seventh cervical nerve. There are only a little over 2 per cent of the plexuses of this type (fig. 6) .
20. In type D, group 2, like type A, there is a branch from the intermediate trunk to the medial fasciculus but there is no branch from the fourth cervical in this type. There is but one example of this arrangement or slightly over one half of one per cent
(fig. 7).
21. Type E, group 2, is exactly like type B, group 1, except there is no branch from the fourth cervical nerve to the plexus. Nearly 30 per cent of the plexuses are of this type (fig. 2) .
22. Type F, group 3, differs from the preceding only in that but part of the fifth cervical joins the plexus. There is a branch from the fifth cervical nerve to the cervical plexus. Slightly less than 7 per cent of the plexuses are arranged in this way (fig. 3) .
23. In type G, group 3, there is a branch from the caudal trunk to the lateral fasciculus, otherwise this is just like the preceding. There is only one specimen of this type (fig. 8).
24. The typical plexuses are those of type B (fig. 1), type E (fig. 2) and type F (fig. 3).
25. In the 63 bodies, 126 plexuses where there are complete records from both sides of the body, the same type of plexus is found on both sides in over 61 per cent.
26. Symmetry is more common than asymmetry in the ratio of about 3 to 2.
27. Asymmetry is found very slightly more often in females than in males.
28. Asymmetry is found most often in white males, least often in colored males, and more often among colored than white females.
29. Symmetry occurred only in the plexuses of type B, E and F which are the most common and typical plexuses of the three groups.
30. Slightly over 71 per cent of the type B plexuses are symmetrical, 60 per cent of the type F and about 54 per cent of the type E.
31. Where asymmetry occurs, the cephalic type of plexus is found on the right side in over 62 per cent.
BRACHIAL PLEXUS OF NERVES IN MAN 371
32. In over 54 per cent of the cases the cephaHc group, type B on one side is associated with an intermediate group, type E on the other.
33. In 12.50 per cent the cephaHc group B is on one side and the caudal group F on the other.
34. The ulnar nerve is formed by the division of the medial fasciculus of the plexus into medial head of the median nerve and the ulnar nerve in over 97 per cent of the cases.
35. There is a lateral head to the ulnar nerve arising from the lateral fasciculus of the plexus, from the lateral head of the median nerve or from the seventh cervical nerve in about 60 per cent of the cases.
36. The ulnar nerve receives its fibers from the eighth cervical and first thoracic nerves probably in all cases, and in those with a lateral head, some fibers from the seventh cervical and possibly some other nerves of the plexus send fibers to it.
37. In the cephalic group of plexuses the ulnar nerve appears to receive fibers from spinal nerves cephalic to the eighth cervical nerve more frequently than in the caudal group.
38. In over 86 per cent of the cases the median nerve is formed by the union of two heads, a lateral head from the lateral fasciculus of the plexus, a medial head from the medial fasciculus.
39. In only one of my cases can I be sure that any nerve that contributes to the brachial plexus did not also send fibers to the median nerve.
40. The musculocutaneous nerve arises from the division of the lateral fasciculus of the plexus into medial head of the median and musculocutaneous nerve in over 88 per cent of the plexuses.
41. In the arm the musculocutaneous gives off a branch that joins the median nerve in 24 per cent of the cases. This is probably a greater percentage than would be found if complete records through the arm had been available for all the cases.
42. The musculocutaneous nerve may receive its fibers from the fourth, fifth, sixth and seventh cervical nerves in 56 per cent of the cases and from the fifth, sixth and seventh cervical nerves only in over 30 per cent, that is fifth, sixth and seventh cervical nerves may contribute in over 86 per cent.
372 ABRAM T. KERR
43. The nerve to the coracobrachiaHs muscle arises from the musculocutaneous in over 40 per cent of the plexuses and from the lateral fasciculus of the plexus in over 20 per cent.
44. The nerve to the coracobrachialis muscle is represented by a single branch in over 55 per cent of the cases; by 2 branches in over 31 per cent; by three branches in over 10 per cent; and by four branches in over 2.5 per cent.
45. In over 84 per cent none of the nerves of the plexus cephalic to the eighth cervical can be excluded from sending fibers to the coracobrachialis muscle.
46. The suprascapular nerve arises from the cephalic trunk of the plexus in over 62 per cent of the cases and from the cephalic trunk or its dorsal or ventral division in over 82 per cent. Fibers of the fifth and sixth cervical nerves may enter the nerve in all of these cases and the fourth also may send fibers in two-thirds of them.
47. The subclavius nerve in nearly 50 per cent of the cases arises from the cephalic trunk of the plexus or its ventral branch. In nearly two-thirds of these the fourth, fifth and sixth cervical nerves may send fibers to it. In over 26 per cent of the cases, it arises from the fifth cervical nerve only and in over 21 per cent it may receive fibers from both fourth and fifth cervical nerves.
48. The subclavius nerve arises as a single branch in over 65 per cent of the cases and from a stem that communicates with the phrenic nerve in over 28 per cent of the cases.
49. The medial brachial cutaneous nerve is represented by a single branch in over 82 per cent of the cases.
50. In over 73 per cent of the cases, the medial brachial cutaneous nerve arises separately. When combined it is most often with the medial antibrachial cutaneous nerve.
51. The fibers of both the first thoracic and eighth cervical nerves may enter the medial brachial cutaneous nerve in over 95 per cent of the cases.
52. Anastomoses of the medial brachial cutaneous nerve with the intercostobrachial is found in over 60 per cent of the cases.
53. In over 82 per cent of the plexuses the medial antibrachial
BRACHIAL PLEXUS OF NERVES IN MAN 373
cutaneous nerve arises from the medial fasciculus of the plexus and in over 10 per cent from the caudal trunk.
54. In over 97 per cent of the cases both the eighth cervical and first thoracic nerves may send fibers to the medial antibrachial cutaneous nerve.
55. The medial anterior thoracic nerve arises from the medial fasciculus in over 69 per cent of the plexuses and from the caudal trunk in over 24 per cent.
56. Both the first thoracic and the eighth cervical may send fibers to the medial anterior thoracic in over 95 per cent of the cases.
57. The lateral anterior thoracic nerve arises from two roots in over 54 per cent of the plexuses, by one root in over 23 per cent and by three roots in nearly 20 per cent.
58. In over 43 per cent of the cases where there is a single root for the lateral anterior thoracic nerve, this comes from the lateral fasciculus of the plexus. In over 78 per cent of the cases where there are two roots, one of them comes from the ventral divisioil of the cephalic trunk and the other from the ventral divisioji of the intermediate trunk (seventh cervical nerve) before these join to form the lateral fasciculus. In ovei- 54 per cent of the cases where there are three roots one arises from the ventral division of the cephalic trunk and the other two from the ventral division of the intermediate trunk of the plexus.
59. In over 52 per cent of the cases the fourth to the seventh cervical nerves can none of them be excluded from the lateral anterior thoracic nerve and in over 30 per cent, .the fifth to the seventh. All of the nerves cephalic to the eighth cervical nerve may send fibers to the lateral anterior thoracic nerve in over 83 per cent of the cases.
60. The radial nerve arises as one of the terminal divisions of the plexus in over 79 per cent of the cases. In the other cases the radial nerve is formed by the union of two heads.
61. In 63 per cent the fourth cervical to the first thoracic nerves can none of them be excluded from the radial nerve and in over 34 per cent the fourth cervical to the first thoracic can not be excluded, that is, in 97 per cent of the plexuses none of the nerves that entered the plexus can be excluded.
374 ABRAM T. KERR
62. The axillary nerve arises as one of the terminal divisions of the plexus in nearly 80 per cent of the cases. In over 9 per cent it arises from the cord formed by the union of the dorsal divisions of the cephalic and intermediate trunks and in the same number of cases from the dorsal division of the cephalic trunk.
63. In over 46 per cent of the cases the axillary nerve gives off none of the other nerves of the plexus but in over 55 per cent it gives origin to the axillary subscapular nerve.
64. None of the nerves from the fourth cervical to the first thoracic can be excluded from the axillary nerve in over 53 per cent of the cases and from the fifth cervical to the first thoracic in over 25 per cent. None of the nerves that enter the plexus can be excluded in over 78 per cent of the plexuses.
65. The subscapular nerve occurs as a single nerve in over 53 per cent of the plexuses. There are two nerves in over 40 per cent and three nerves in over 5 per cent of the plexuses.
66. One of the subscapular nerves arises from the dorsal division of the cephalic trunk of the plexus in over 56 per cent of the cases; from the dorsal division of the intermediate trunk in over 19 per cent and from the posterior fasciculus in over 28 per cent.
67. In over 61 per cent of the cases the fourth cervical nerve may send fibers to the subscapular nerve ; in over 94 per cent the fifth and sixth cervical nerves ; and in over 50 per cent the seventh cervical nerve.
68. The axillary subscapular nerve arises directly from the posterior fasciculus of the plexus or from the axillary nerve or the radial nerve that arise from the posterior fasciculus in over 74 per cent of the cases. It comes from the dorsocephalic cord formed by the union of the dorsal divisions of the cephalic and intermediate trunks in over 13 per cent.
69. The axillary subscapular nerve arises directly from one of the dorsal divisions of the brachial plexus in over 45 per cent of the cases and from the axillary nerve in over 54 per cent.
70. None of the nerves of the plexus can be positively excluded from the axillary subscapular in over 72 per cent of the cases.
BRACHIAL PLEXUS OF NERVES IN MAN 375
The nerves caudal to the seventh cervical can be excluded in 23 per cent of the cases.
71. The thoracodorsal nerve arises either directly from the posterior fasciculus of the plexus or from a nerve that takes origin from the posterior fasciculus in over 70 per cent of the plexuses. In over 5.5 per cent of the cases it arises from the radial nerve and in the same number from the axillary nerve.
72. In over 71 per cent, none of the nerves of the plexus can be positively excluded from sending fibers to the thoracodorsal nerve.
LITERATURE CITED
Adolphi, Hermann 1898 Ueber das Verhaltenden des zweiten Brustnerven
zum Plexus brachialis beim Menschen. Anat. Anz., Bd. 15, pp. 98-104. Bardeen, Charles R. 1900 Outline Record Charts used in the Anatomical
Laboratory of the Johns Hopkins University. The Johns Hopkins
Press. Baltimore.
1901 A statistical study of the variations in the formation and position
of the lumbosacral plexus in man. Anat. Anz., Bd. 19, pp. 124-135, 209 238 Birmingham, A. 1895 The nerve of Wrisberg. Jour. Anat. and Physiol., vol.
20, p. 63. Cunningham, D. J. 1877 Note on a connecting twig between the anterior
divisions of the first and second dorsal nerves. Jour. Anat. and
Physiol., vol. 11, p. 539. EcKHARD, C. 1862 Lehrbuch der Anatomie des Menschen, p. 332. Harman, Bishop 1900 The anterior limit of the cervicothoracic visceral
efferent nerves in man. Jour. Anat. and Physiol., vol. 34, pp. 357-380. Harris, Wilfred 1903 Prefixed and postfixed types of brachial plexus. 'Brain,
vol. 26, pp. 613-615.
1904 The true form of the brachial plexus, and its motor distribution.
Jour. Anat. and Physiol, vol., 38, pp. 399-442. Herringham, W. p. 1887 The minute anatomy of the brachial plexus. Proc.
Roy. Soc. London, vol. 41, pp. 423-441. Kaufmann, Fr. 1864 Die VarietJiten der Plexus brachialis, Giessen. Kerr, AbramT. 1907 Statistical studies of the brachial plexus in man. Anat.
Rec, vol. 1, p. 53. Lucas, R. Clement 1875 On the normal arrangement of the brachial plexus
of nerves. Guys Hospital Reports. London, 3CXX pp. 539-546. Paterson, a. M. 1896 A discussion of some points of the distribution of the
spinal nerves. Jour. Anat. and Physiol., vol. 30, pp. 530-538. Schumacher, Siegmund V. 1908 Zur Kenntnis der segmentalen Innervation
der oberen Extremitiit des Menschen. Sitzungs d. Kaiserl. Akad. der
Wissensch. tVein 117, pp. 131-209.
376
ABRAM T, KERR
Scott, Sidney 1906 A record of the decussation of the brachial plexus. Jour.
Anat. and Physiol., vol. 40, pp. 412-415. ViLLAR, F. 1888 Quelques recherches sur les Anastomoses des nerfs du membre
superieur. Bull. Soc. Anat. de Paris, pp. 607-615. W.^LSH, J. F. 1877 The anatomy of the brachial plexus. Am. Jour. Med. Sci.
N. S. 74, pp. 387-399. WiCHMANN, Ralf 1900 Die Riickenmarksnerven und ihre Segmentbeziige.
Berlin.
TiBLE 1
Showing the distribution of 175 brachial plexuses as to sex, color and side of the body
White
Colored
Right
Left
_., /Right. ^^^^*^ \Left ..
Colored if'f' l^Left. .
Total
Number
65 49 56 58 33 32 23 26
114
Per cent
37.14 28.00 32.00 33.14
18.85 18.28 13.14 14.85
65.14
Number
20 41 31 30 9 11 22 19
61
Per cent
11.42 23.42 17.71 17.14 5.14 6.28 12.57 10.85
34.85
MALE AND FEMALE
Number
85 90 87 88 42 43 45 45
175
Per cent
48.57 51.42 49.71 50.28 24.00 24.57 25.71 25.71
100.00
TABLE 2
Showing the distribution as to sex, color, and side of the body of the 110 brachial
plexuses of Group 1
White
Colored
Right
Left.
Colored {^^^\ Total
Number
41 29
34 36 20 21 14 15
70
Per cent
37.27 26.36 30.90 32.72 18.18 19.09 12.72 13.63
63.63
Number
15 25 20 20 6 9 14 11
40
Per cent
13.63 22.72 18.18 18.18 5.45 8.18 12.72 10.00
36.36
M,\LE AND FEM.\LE
Number
56 54 54 56 26 30 28 26
110
Per cent
50.90 49.09 49.09 50.90 23.63 27.27 25.45 23.63
100.00
BRACHIAL PLEXUS OF NERVES IN MAN
377
TABLE 3 Showing the distribution as to sex, color, and side of the body of the 52 brachial
plexuses of Group 2
Number
Per cent
Number
Per cent
MALE AND FEMALE
Number
Per cent
White
Colored
Right
Left
White |-^'^^*- •
Colored Iff* l^Left. .
Total
18 17 19 16 11 7
34.61 32.69 36.53 30.77 21.15 13.46 15.38 17.30
3
14 9
8 2 1
7 7
5.76 26.92 17.30 15.38 3.84 1.92 13.46 13.46
35
67.30
17
32.69
21 31 28 24 13 8 15 16
52
40.38 59.61 53.84 46.15 25.00 15.38 28.82 30.77
100.00
TABLE 4
Showing the distribution as to sex, color, and side of the body of the 13 brachial
plexuses of Group 3
MALE
FEMALE
MALE AND FEMALE
Number
Per cent
Number
Per cent
Number
Per cent
White
6 3
9
6 2 4
1 2
46.14 23.07 23.07 46.14 15.38 30.76 7.69 15.38
2 2 2 2 1 1 1 1
15.38
15.38
15.38
15 38
7.69
7.69
7.69
7.69
8 5 5 8 3 5 2 3
61 53
Colored
38 46
Right
38 46
Left
61.53
„Ti ., f Right
23.07
Wb^^nLeft
38 46
^ , , f Right
15 38
C^^^-^Left
23.07
Total
9
69.23
4
30.76
13
100,00
378
ABRAM T. KERR
TABLE 5 Showing distribution among the three groups of the 114 plexuses fro7n male subjects
GROUP 1
GROUP 2
GROUP 3
White
41 29 34 36 20 21 14 15
35.96 25.43 29.82 31.57 17.54 18.42 12.28 13.15
18
17
19
16
11
7
8
9
15.78
14.91
16.66
14.02
9.64
6.14
7.01
7.89
6
3 3 6 2 1 4 2
5.26
Colored
Right
2.63 2.63
Left
„„ . f Right .
5.26 1 75
«"*<' iLeft
^ , , [Right
0.87 3.50
Col^-^lLeft
1.75
Total
70
61.40
35
30.70
9
7.89
TABLE 6 Showi7ig distribution among the three groups of the 61 plexuses from female subjects
GROUP 1
GROUP 2
GROUP 3
White
15 25 20 20 6 9
14 11
24.59 40.98 32.78 32.78 9.83 14.75 22.95 18.03
3
14
9
8 2
1
7 7
4.92 22.95 14.75 13.11 3.27 1.63 11.47 11.47
2 2 2
2 1 1 1
1
3.27
Colored
Right
Left
[Right
3.27 3.27 3.27 1.63
White T 1
[Left
Colored {S'
1.63 1.63 1.63
Total
40
65.57
17
27.86
4
6.55
TABLE 7 Showing the distribution among the three groups of the 85 plexuses from white subjects
'
GROUP 1
GROUP 2
GROUP 3
Male
41 15 26 30 20
6 21
9
48.23 17.64 30.58 35.29 23.52 7.05 24.70 10.58
18 3
13 8
11 2
7 1
21.15 3.52
15.29 9.41
12.94 2.35 8.23 1.17
6 2 3 5 2 1 4 1
7.05
Female
2.35
Right
3.52
Left
5.88
.„. , / Male
2.35
^^^^n Female
1.17
., „ f Male
4.70
Left< „ ,
1 remale
1.17
Total
56
65.88
21
24.70
8
9.41
BRACHIAL PLEXUS OF NERVES IN MAN
879
TABLE 8 Showing the distrihution among the three groups of the 90 plexuses from colored
subjects
Male
Female
Right
Left
^. ,^ /Male...
^'^^ \Female
j^^jjMale....
\ Female. .
Total
29 25 28 26 14 14 15 11
54
32.22
27.77 31.11 28.88 15.55 15.55 16.56 12.22
59.99
GROUP 2
17 14 15 16
8 7 9
31
18.88 15.55 16.66 17.77
8.88
7.77
10.00
7.77
34.44
3.33 2.22 2.22 3.33 1.11 1.11 2.22 1.11
ii.oo
TABLE 9 Showing the distribution among the three groups of the 87 plexuses from the right
side of the body
GROUP 3
Male
Female
White
Colored
Male ^^^'*^
^^^^ \ Colored .,
T. , [White..
I'emale < ,-, , ,
(^Colored
Total
34 20 26 28 20 14 6 14
54
39.08 22.98 29.88 32.18 22.58 16.07 6.89 16.09
19
9
13
15
11
8
2
7
62.06
28
21.83
10.34
14.94
17.24
12.64
9.19
2.29
8.04
32.18
3.44 2.29 3.44 2.29 2.29 1.14 1.14 1.14
5.74
TABLE 10 Showing the distribution among the three groups of the 88 plexuses from the left side
of the body
GROUP 1
GROUP 2
GROUP 3
Male
36 20 30 26 21 15 9 11
38.63 22.72 34.09 29.54 23.86 17.04 10.22 12.50
16
8
8
16
7 9
1
7
18.18 9.09 9.09
18.18 7.95
10.22 1.17 7.95
6 2 5 3 4 2
1 1
6 81
Female
2.27
White
5 68
Colored
3 40
,, , [White
4.54
Multicolored
2.27
T, , [White
1.13
^""'^'^ [Colored
1.13
Total
56
63.63
24
27.27
8
9 09
380
ABEAM T. KERK
TABLE 11
Shoiving the relative size of the nerves of the brachial plexus in the 27 cases that were
measured
TYPE
TYPE
OP
OF
PLEXUS
PLEXUS
5C
<
IT
<
6C
<
70
=
80
c
50
=
IT
<
60
=
80
<
70
5C
<
IT
<
6C
<
70
=
80
50
=
IT
<
60
=
80
<
70
5C
<
IT
<
6C
=
70
<
80
50
=
IT
<
60
=
70
=
80
5C
<
IT
<
6C
<
80
<
70
G
50
=
IT
<
60
=
70
=
80
5C
<
IT
=
6C
<
70
=
80
50
=
IT
=
60
<
70
=
80
F
5C
<
IT
=
6C
<
70
=
80
B
50
=
IT
<
70
<
60
<
80
5C
<
IT
=
6C
<
80
<
70
G
IT
<
50
<
60
=
70
<
80
G
5C
<
IT
=
6C
=
70
=
80
F
IT
<
50
<
60
=
70
<
80
5C
<
IT
=
7C
<
80
<
60
F
IT
<
50
<
80
<
60
=
70
5C
<
IT
<
80
<
60
<
70
IT
<
50
=
80
<
60
<
70
5C
<
IT
<
8C
<
60
=
70
IT
<
50
=
80
<
70
<
60
5C
=
IT
<
6C
<
70
<
80
IT
<
60
<
50
<
70
=
80
5C
=
IT
<
60
<
70
<
80
IT
<
80
<
50
=
60
=
70
5C
=
IT
<
60
<
80
<
70
EXPLANATION OF FIGURES
The drawings for this article, with one exception, were made by Mrs. Kerr. They are semidiagrammatic sketches. The plexuses from the right side have been reversed to render comparison easier. Figures 1 to 8 and 29 are two-thirds natural size and figures 10 to 2 are one-half size. Figure 9 drawn by Miss Whitman from the macerated specimen is reduced to about natural size.
mus. cuta.
Sx:^-med.
med. antibr. cuta'.
ax. subscap.
Fig. 1 From the right side of a white female, age 73 years, reversed. Group 1, Type B.
Fig. 2 From the right side of a colored female, age about 60 years, reversed. Group 2, Type E.
3S1
THE AMERICAN JOUBNAL OF ANATO.Mr, VOL. 23, XO. 2
thor. dors: med. ar
ax. subscab.
C.4 1 -^ — _^ - .supra, clav, C.s /*^r^ , to phren
suprascap
lat. ant. thor.
cor. br.
subscap!
med. br. cuta. - ,
med. ant. thor'. . ^^
ax. subscap.
med. antibr. cuts.
mus. cuta.
med.
uln.
Fig. 3 From the right side of a white male, age about 35 years, reversed, -oup 3 Fig.' Type A.
^Tig. 4 ^Fr^om^the right side of a white female, age 95 years, reversed. Groupl,
382
C.4
C.6
C.T C. 8
Th.i
suprascap
lat. ant. thor.
mus. cuta.
med. br. cuta.- med. ant. thor. '
med. antibr. cuta.
subscap.
med.
thor. dors;
ax. subscap.
supra, clav.
lat. ant. thor.
subscap
cor. br.
med.
med. br. cuta. ^^^-,uln.
med. antibr. cuta.
Fig. 5 From the left side of a colored female, age 14 years. Group 1, Type A. Fig. 6 From the left side of a white male, age about 40 years. Group 1, Type C
383
mus. cuta.
med.
"••uln.
C.4 fe:i^5r^
supra, clav.
.. suprascap.
--^.^e ^ ,3^^ ant. thor.
cuta.
med.
Fig. 7 From the left side of a white male. Group 2, Type D. Fig. 8 From the left side of a colored male, age 25 to 30 years. Group 3, Type G.
384
BRACHIAL PLEXUS OF NERVES IN MAN
385
Fig. 9 Showing the connections and interlacings of the funiculi of a plexus as they appeared after the connective tissue was removed by maceration.
386
ABRAM T. KERR
supra, clav.
ax. subscap'.
thor. dors.
10
11
Fig. 10 From the loft side of a white male, age 35 years. Group 2, Type F. Fig. 11 From the left side of a colored female. Group 1, Type B.
BRACHIAL PLEXUS OF NERVES IN MAN
387
to phren 2nd intercosto.
med. antibr. cuta.
Fig. 12 From the right side of a colored female, age 25 to 30 years, reversed. Group 1, Type A.
Fig. 13 From the right side of a colored female, age 30 years, reversed. Group 1, Type B.
388
A BEAM T. KERR
lat ant. thor.
rad.
14
med. ant thop. .^^ . VN/X. ^*"V.
\ >^
med. antibr. cuta. ', '■ -^^^
V N. mus. cuta. ^^j^ med.
thof. dors; • n/^
\
subscap! ax. subscap.
ulo.
c. »
Th.;
Fig. 14 From the left side of a white female, age 61 years. Group 2, Type E. Fig. 15 From the right side of a white male, age 60 years, reversed. Group 2, Type E.
BRACHIAL PLEXUS OF NERVES IN MAN
389
subclav.
lat ant. thor. ra^.
lat head uln. cor. br. /■ mus. cuta.
med. br. cufa.. 2nd intercosto. br..-. med. antibr. cuta..
thor. dors;
Fig. 16 From the right side of a white male, age 55 years, reversed. Group 2, Type E.
Fig. 17 From the left side of a colored male, age 20 to 25 years. Group 1, Type B.
390
ABRAM T. KERR
18
ax. subscap:
C. 7 C. ,
m 1
ax. subscap.' m^l- anW"^- c^^.
Fig. 18 From the right side of a colored male, age 20 to 25 years, reversed. Group 1, Type B.
Fig. 19 From the right side of a white male, age 55 to 60 years, reversed. Group 1, Type B.
BRACHIAL PLEXUS OF NERVES IN -MAN
391
to phren.
C, Q
C. 8 Q
lat. ant. thor.
med. br. cuta.-.. --med. antibr. cuta.
20
21
med. antibr. cuta.
Fig. 20 From the right side of a white male, age about 40 years, reverse^ Group 1, Type B. "
Fig. 21 From the left side of a white male, age about 70 years. Group 2, Type F.
392
ABEAM T. KERR
lat. ant. thor.
ax. subscap.
med. antibr. cuta.
laL ant. thor.
Fig. 22 From the right side of a white male, age 38 j'ears, reversed. Group 2, Type E.
Fig. 23 From the right side of a colored male, age 45 years, reversed. Group 1. Type B.
BRACHIAL PLEXUS OF NERVES IN MAN
393
to phrea
lat. ant thor.
med. br. cuta.
thor. dors, med. antibr. cuta.
ax. subscap.
24
to phren.
.. C
C. Th.i
2nd Intercosto. br.
med. br. cuta..
med. antibr. cuta.
Fig. 24 From the right side of a colored male, age about 25 years, reversed. Group 1, Type B.
Fig. 25 From the right side of a colored male, age 35 years, reversed. Group 2. Type E.
394
ABRAM T. KERR
to ptiren.
26
med. antibr. cuta. "•, ax. subscap.
med.
C.I
Th.
27
med. antibr. cuta.
Fig. 26 From the right side of a colored male, reversed. Group 2, Type E. Fig. 27 From the right side of a colored male, age 40 years, reversed. Group l.TypeC.
BRACHIAL PLEXUS OF NERVES IN MAN
395
28
thor. dors, med. br. cuta.
med. antibr. cuta.
■■,uln.
2nd intercosto. br.
thor. dors.— ' med. fasc. ;
ax. subsca'p.
med. antibr.
Fig. 28 From the left side of a colored male, age 40 years. Group 1, Type C. Fig. 29 A composite, typical plexus.
AUTHOR S ABSTRACT OF THIS PAPER ISSDED BY THE BIBLIOGRAPHIC SERVICE, DECEMBER 29
ON THE AGE OF HUMAN EMBRYOS
FRANKLIN P. MALL
Johns Hopkins Medical School, Baltimore, Md.
TWO FIGURES AND EIGHT TABLES
In the Manual of Human Embryology, published seven years ago, I presented the evidence by which we may determine the age of an embryo or fetus, in my chapter dealing with this subject. ^ It was there pointed out that the best che«k in arranging embryos in time sequence is obtained from our knowledge of comparative embryology; also, that the only factor which can be depended upon in every case is what I then termed the 'menstrual age;' that is, the age of the embryo as computed by the time elapsing between the beginning of the last menstrual period and the date of the abortion.
In order to procure a satisfactory curve of growth for the whole period of gestation, I succeeded in collecting about 1000 specimens from the different months of pregnancy with the data given concerning them; namely, the measurements of the embryos and the dates of menstruation and of abortion. It was also necessary to establish standard measurements for the embryos, chief of which are sitting-height and standing-height;
1 Mall, Franklin P. 1910 Determination of the age of human embryos and fetuses. Manual of Human Embryology, Chap. 8. Edited by Franz Keibel and Franklin P. Mall, Philadelphia; German edition, Leipzig, 1910.
1903 See also Note on the collection of human embryos in the Anatomical Laboratory of the Johns Hopkins University. Johns Hopkins Hospital Bulletin, vol. 14.
In the second paper I gave a formula by which the age of embryos up to 100 mm. long could be determined. That is, to multiply the CR length in millimeters by 100 and extract the square root ; the product is the age in days. I wish to state that this formula gives the age according to the His convention, which I now believe to be incorrect, as demonstrated in my chapter in the Manual. This conclusion was also reached independently by Bryce and Teacher.
A fairly complete bibliography is to be found in the papers b}^ Mall (1), Bryce and Teacher (3), Triepel (2) and Grosser (6).
397
THE AMERICAN JOURNAL OF ANATOMY, VOL. 23, NO. 2
398 FKANKLIN P. MALL
t^ese are known respectively as crown-rump {CR) and crownheel (CH). Tables were prepared by which the average measurements of the' one for a given stage could be converted into the average measurements of the other; for it is well known that embryologists are given to using the crown-rump measurement for smaller specimens, while anthropologists and obstetricians generally use the crown-heel measurement for larger specimens.
MENSTRUATION AGE
My tabulation of the menstrual age was made as follows: All the measurements of the embryos and fetuses were converted into crown-rump or sitting-height measurements. These were then used as ordinates, while the menstrual ages were used as abscissae; in other words, each specimen was entered upon a chart in which the menstrual age and the vsitting-height together made a co-ordinate. In this way the 1000 specimens were spread over a millimeter chart, 500 mm. high and 350 mm. wide. It was found that the individual records arranged themselves along a path about 20 mm. wide at the base line, and about 40 mm. wide toward the upper margin of the chart. In addition to this central zone containing most of the records there were numerous scattered entries far out of line. These were especially numerous at the bottom of the chart, which would indicate that in early abortions there is an undue number of poor records ; or, at least, records showing greater irregularity in the menstrual periods. In order to determine a mean menstrual age the chart was marked square by square in such a way that exactly onehalf of the records were circumscribed by two lines enclosing the usual or normal cases, leaving one quarter of the scattered records to tlje right of one line, the other quarter to the left of the other line. The first group includes those specimens which grew very slowly and may have been pathological; the second, those cases in which menstruation continued after pregnancy. The two lines which include the middle group are practically parallel, beginning about 20 mm. apart, around the records of the early specimens, and ending about 40 or 50 mm. apart around the specimens from the latter part of pregnancy. The distance
AGE OF HUMAN EMBRYOS 399
between these two lines was then divided exactly, and it is this line which marks the mean menstrual age of embryos throughout pregnancy. In a general way it is reproduced as the line CH in figure 145 in the Manual of Human Embryology (p. 200).
1 have spoken of the age thus determined at different times as the menstrual age, or more properly speaking the mean menstrual age, because there is a very large probable variation. For instance, a number selected at random from the table on page 199 of the Manual, with a mean menstrual age of 51 days, would also show a probable deviation of from 40 to 62 days. Such embryos have a height of 11 mm.; therefore, when we obtain embryos of this length, we may expect that one-half of them have a menstrual age of from 40 to 62 days; in other words, in small specimens there is a probable variatioii of three weeks. Viewed from another angle, one-half of the embryos with a menstrual age of 51 days w^ould range from 4 to 25 mm., while the average would be 11 mm.; hence, we are probably dealing with a pretty large error which cannot be definitely locatecT. At present it would appear that pregnancy may begin at any time during the intermenstrual period, but it is difficult to determine the most probable time. What I published in the Manual has received careful criticism from Triepel,- but he nevertheless also accepts the term menstrual age, and recommends that we use it in the future.
COPULATION AGE
After constructing the curve and table referred to above, showing the mean menstrual age, I entered as the probable or true age a line in the curve and a column in the table which fall in a position exactly ten days earlier than the mean menstrual age. This was done for the following reasons : According to the more recent statistics of Issmer, that writer found the average duration of pregnancy in 1220 cases to be 280 days, when estimated from the first day of the last menstrual period; and in 628 cases, 269 days when estimated from fruitful copulation. In general these figures correspond with those of Ahlfeld, Hecker
2 Triepel, A. 1915 Alterbestimmung bei menschlicheu Embryonen. Anat. Anz., Bd. 46, 1914. Also Bd. 48.
400 FRANKLIN P. MALL
and Hasler, who collected about 500 cases in which the date of fruitful copulation was given. Therefore, in a group of 1200 cases the duration of pregnancy, when reckoned from the last menstrual period, was fully ten days longer than when computed from the time of copulation; and it seems to me that in order to determine the true age it is necessary to deduct these ten days from the menstrual age. Even then I believe we should be careful not to use the word true, since the time of copulation does not necessarily record the time of fertilization. For this reason it might be well if we introduced the term, copulation age, to distinguish it from menstrual age, and from two other ages I am about to give. These could be termed ovulation age and fertilization age, the latter being the only true age, since we must always figure the beginning of development from the time of fertilization.
The curve in the chart, which I gave in my publication, as representing the true age, but which I now will speak of as the copulation age, was constructed from cases of newborn children, and is probably the more . valuable because it eliminates all of the irregularities of early pregnancy which accompany natural abortion. After the curve was completed, however, we received into our collection a few embryos, measuring less than 25 mm., the accompanying records of which gave the time of copulation as well as of menstruation. The copulation ages of these specimens were then entered upon the chart shown in the IVIanual with stars (fig. 147), and curiously enough nearly all of them fall exactly upon the line of the curve, showing that what was assumed to be a difference at the end of pregnancy is also indicated again in specimens from the beginning of pregnancy. In both cases the difference between the menstrual age and the copulation age is about 10 days. When this chart was made it contained seven stars, but after it had been sent to the printer I found another case in the literature. Also, about the same time I received a copj^ of a book published by Bryce and Teacher,^ which gave a second case, and these were added to the curve.
^ Bryce and Teacher 1908 Contributions to the study of the early devcktpment and imbedding of the human ovum. Glasgow.
AGE OF HUMAN EMBRYOS 401
To my great surprise and pleasure I found that these authors had reached a conclusion similar to mine; namely, that the age of young embryos is no longer to be computed according to the convention of His. They not only give a detailed and excellent account of their own specimen, but also reconsider all other cases of young specimens in relation to their age, which have been published by well-known writers. They assume that the copulation age is probably very nearly the true age of embryos, and that henceforth we will have to consider the question from this standpoint.
According to Bryce and Teacher, it is now generally admitted that the menstrual cycle in man and monkeys is homologous with the oestrus cycle of the lower mammals. The oestrus cycle is divided by Heape into pro-oestrum, oestrus and dioestrum, and this division has been confirmed for many mammals by his own researches and those of F. H. A. Marshall. During prooestrum the generative organs of the female show signs of special activity, such as swelling of the vulva, coloration or flushing of the surroundings, and a discharge of blood or mucus from the vagina. This is immediately followed by the 'oestrus,' or 'period of desire,' during which alone the female is capable of impregnation and will receive the male. If pregnancy does not occur, oestrus, after a brief space in which desire subsides (metoestrum), is succeeded by a period of quiescence or dioestrum, which lasts till pro-oestrum again sets in. In polyoestrous mammals several cycles of this kind may follow one another. Menstruation in the human female is homologous with pro-oestrum, as first pointed out by Heape. Though there is no fixed 'period of desire' there is an indication that a vestige of this persists, in the fact that a phase of more pronounced oestrus commonly succeeds the cessation of menstruation. This view is confirmed by our records, for we frequently hear from a patient that a fruitful copulation occurred shortly after the menstrual period; and it may be that this opinion records also the rupture of the Graafian
402 FRANKLIN P. MALL
follicle. According to J. G. Clark^ this is accompanied by vascular hyperemia of the ovary, and the possibility of a spasm of the ovary is not to be excluded, for there is an abundance of muscle in this organ which no doubt has a function to perform.
The following histories include all cases from our collection in which the copulation history is given. I have also added the Watt^ case because it is the only one I have been able to find in the literature since the publication of the Manual. I have included all cases because I think it is best not to select those which suit my convenience in making a curve, but to give the poor material together with the good. A few of the records are sufficiently complete to be unimpeachable; the remainder are given for what they are worth.
No. 1399
(Dr. H. N. Mateer, Wooster, Ohio.)
Embryo, GL 1 mm. Chorion 10 x 9 mm. From a hysterectomy. Copulation September 19 and September 27. Operation, October 19. (I have been unable to find out date of last period, but it is probably recorded.) Copulation age 22 or 30 days. If the former is taken, it matches the curve exactly.
No. 779
(Dr. , Baltimore.)
Embryo, GL 2.75 mm. The specimen though otherwise normal was later found to have spina bifida. It came from the physician's wife. She is 37 years old, and is the mother of one child and this is her first abortion. She is very anxious to have children. Last period, August 29 to September 2. Abortion, October 12. Fruitful copulation, in the woman's opinion, September 25 and later. She does not state specifically that copulation occurred between September 2 and September 25. Menstrual age, 44 daj^s. Copulation age, 17 days or less. Doubtful case.
^ Clark, J. G. 1899 The origin, growth and fate of the corpus luteum as observed in the ovary of the pig and man. Johns Hopkins Hospital Reports, vol. 7.
1900 The origin, development and degeneration of the blood-vessels of the human ovary. Johns Hopkins Hospital Reports, vol. 9.
^ Watt. J. B. 1915 Description of two twin human embryos with 17 to 19 paired somites. Contributions to Embryology, vol. 2, Carnegie Institution of Washington, Publication No. 222.
AGE OF HUMAN EMBRYOS 403
Watt's case
(Dr. Watt, Toronto.)
Twin embryos, GL 2.75 and 3.55 mm.
Mother, a German Jewess, 30 years old, robust and healthy, four children and this one abortion. Last period, December 3 to 6, 1907; first copulation December 20. Slight flow January 3, with similar flow on January 11, 12 and 13, abortion following on January 14. Menstruation age, 42 days. Copulation age, 25 days or less.
No. 1182 b
(Dr. C. E. Caswell, Wichita, Kansas.)
Woman aged 27, four living children and one abortion. Husband has syphilis and so has one child. Mother seems to have escaped. Last period, March 25 to April 4. Abortion, May 10. Mother is sure that conception took place April 14. Menstrual age 46 days. Copulation age, 26 days. Doubtful case.
No. 470
(Dr. H. C. Ellis, Elkton, Md.)
Embryo, CR 4 mm. Chorion, 20 x 13 mm.
Mother, 24 years old, two healthy children. Abortion during an attack of mumps with very high fever. Last period October 5, 1910, and copulation about October 15. Abortion November 9. Menstrual age, 35 days; copulation age not over 25 days.
No. 588
(Dr. G. L. Wilkins, Baltimore.)
Embryo, CR 4 mm.
Last period January 26 to February 3. Had no intercourse with husband for several weeks prior to this and only three or four days after period but not later. Abortion March 16, 1912. She has had two healthy children, 14 and 20 years old respectively, and not less than eleven abortions. Dr. Wilkins believes that all the abortions were induced. Menstrual age, 50 days. Copulation age, 38 or 39 days.
No 1507
(Dr. C. B. Ingraham, Denver, Colorado.)
Macerated embryo, GL 4 mm.
A Jewess who last menstruated May 7 to 11; abortion June 22.
Woman had opportunity to become pregnant shortly after this period
or again just before the next. Menstrual age, 46 days; copulation age,
40 days or 17 days. Record not satisfactory, especially since specimen
s also pathological.
404 FRANKLIN P. MALL
No. 208
(Dr. J. Y. Dale, Lamont, Pa.)
Normal embryo, CR 7 mm., GL 8 mm. The specimen was enclosed in an almond-shaped ovum, measming 22 x 11 x 11 mm., and there x was considerable magma within the exocoelom. The specimen came from a married woman whose last period began on Etecember 28, 1901, and who had coitus only twice, January 5 and January 7, between this period and the time of abortion, February 15, 1902. Dr. Dale informs me that the data are entirely reliable, as both the woman and her husband are thoroughly trustworthy. The specimen was secured for me by Prof. John G. Clark of the University of Pennsylvania, who thought that its unique historj^ gave it greater value. Menstrual age, 49 days; copulation age, 39 to 41 days.
No. 1461
(Dr. H. A. Wiight, Seattle, Washington.) Embryo, CR 9.8 mm.
Menstrual age, 28 days; copulation, 27 days. Data inaccurate and incomplete. Not a reliable case.
No. 443
(Dr. William Grant, Baltimore.)
Embryo about 10.5 mm. long.
The specimen was sent at the suggestion o^ Prof. T. S. Cullen on account of its interesting history. Menstrual age, 27 days and copulation age, 28 days. On account of the manner in which the history was given, and because of the degree of development of the embryo, the data can hardly be admitted as correct. The husband had been away from home for four months prior to the time of coitus, which was on the last day of menstruation. The woman is the mother of four healthy children and menstruates regularly every 28 daj^s. The patient was reluctant to show the specimen to the physician, and both she and her family defended her character, a fact which would seem still further to convict her. For this reason the record is not to be considered reliable so far as the age of the embryo is concerned.
No. 167
(Dr. A. H. Ritter, Brooklyn, N. Y.)
Embryo, CR 14.5 mm., NL 13.5 mm.
The normal embryo was sent in a beautiful normal ovum measuring 30 X 30 X 20 mm. The specunen came from a multipara whose last period was from November 26 to December 2, 1899. First copulation
AGE OF HUMAN EMBRYOS 405
after the period on December 15. Due to a surgical operation on January 24 there was continuous hemorrhage until January 3 when the ovum was passed. In the event that conception took place after the last period, this specimen could not be more than 46 days old. Menstrual age, 65 days; copulation age, 46 days.
No. 1390
Dr. G. N. J. Sommer, Trenton, N. J.)
Embryo CR 18 mm.
Last period, December 18 to 22. Operation for tuba^ pregnancy, February 10. Conception took place on December 25, as the woman was in the habit of using preventive means and same were not used on Christmas eve. Menstrual age, 54 days; copulation age, 47 days. Reliable case.
No. 1584
(Dr. F. H. Church, Bonnville, N. Y.)
Embryo, CR 18 mm. Chorion 35 x 31 x 25 mm.
Unmarried woman, age 21, first pregnancy. Last period August 15; menstruation regular, every 28 days. Criminal abortion, October 10. Coitus, September 13 and 14. Menstrual age, 56 days; copulation age, 26 and 27 days. Not Reliable.
No. 26.
(Dr. C. E. Simon, Baltimore.)
Fetus, CR 25 mm., CH 30 mm. This specimen, which was somewhat injured and therefore difficult to measure with precision, was brought to me by Dr. Simon, February 25 (?) 1894 with the following history. The mother, an unmarried woman 27 years old, was a servant in Dr. Simon's family, and had but recently come from Germany. She remained at home continually until New Year's eve, when she went to a ball and remained out all night. Her last 'period took place on December 12 and lasted six days. During the night of December 31 she was with her lover and the abortion followed on February 25. On January 16, after missing her January period, she took a cupful of mustard powder with the hope that it would produce abortion, but instead it yearly killed her. On January 21, she recovered, and resumed her household duties. (See record of the case by Simon, N. Y. Med. Jour., March 17, 1894.) Later she fell into the hands of an abortionist and the embryo came away during the night of February 24. Dr. Simon assured me al: the time of the abortion that it was absolutely impossible for the pregnancy to have taken place at any time excepting the night of December 31.
Menstrual age, 75 days; copulation age, 56 days. Reliable case.
406 FRANKLIN P. MALL
No. 616
(Dr. S. P. Warren, Portland, Me.)
Embrj^o, CR 26 mm. Unmarried woman, 18 years old; last period began August 9 and continued 7 days. Coitus three times within 9 days after the last period. Curetted after 24 hours of pain, October 13, 1912.
Menstrual age, 65 days; copulation age, 56 days (?). Not reliable.
No. 1535
(Dr. PhiHp F. WilKams, Philadelphia).
Embryo, CR 28 mm. Chorion, 50 x 45 x 15 mm.
Unmarried woman, 20 years old; first pregnancy. Last period, May 3 to 7. Abortion, July 6. Last coitus. May 10 (?). Menstrual age, 62 days; copulation age, 55 days. Doubtful age, but it falls close to the time of the probable age.
No. 373
(Specimen loaned by Prof. Simon H. Gage, Ithaca, N. Y., Cornell Collection, Homo No. 11.)
Embryo, CR 31 mm.
Last period. May 9. Conception, May 21. Natural miscarriage July 17, after 2 to 3 days bleeding. No other data. According to these records the menstrual age is 69 days and the copulation age 57 days.
No. 849
(Dr. Shipley, Baltimore.)
Embryo, CR 52.5 mm.
Mother, white, unmarried, age 20. Last period, December 11 to 15, 1913. Abortion, March 3. Coitus from which mother dates pregnancy occurred just after the cessation of the last menstrual period in December, but she admits that she had frequent intercourse previous to this period.
Menstrual age, 82 days; copulation age, 77 daj's (?) Doubtful case.
No. 591
(Dr. G. C. McCormick, Sparrows Point, Md.) Embryo, CR 62 mm. End of last period, January 1, 1*)12. Coitus, January 7; abortion, March 29.
Menstrual age, 93 days; copulation age, not over 82 days.
No. 1635
(Dr. Henry Leaman, Philadelphia.)
Embryo, CR 70.5 mm. Mother, 40 years old, 9 children. Last
AGE OF HUMAN EMBRYOS 407
period, August 26 to 30; abortion, November 29. Copulation but •once about September 3 to 15. Self induced abortion.
Menstrual age, 95 days; copulation age, 75 to 87 days. Records contradictory.
No. 322
(Dr. West, Bellaire, Ohio.)
Embryo, CR 85-90 mm.
The specimen is probably from an induced abortion. The mother says that fruitful coitus took place on June 17 and the abortion on September 20, copulation age 95 days.
No. 1295 c
(Dr. L. J. Commiskey, Brooklyn, N. Y.)
Embryo, CR 87.
Woman, 43 years old, mother of one child and this is her second abortion. Last period, April 24 to 28; abortion, July 27. Woman states with great certainty that the productive coitus took place either May 4 or 6.
Menstrual age, 94 days; copulation age, 84 or 82 days. Doubtful case.
No. 1310
(Dr. B. G. Pool, Washington, D. C.)
Embryo, CR 95 mm.
First pregnancy of unmarried woman, 18 years old. Last period, July 25 to 30, 1915; abortion, November 6. Said to be from a single coitus on August 9. Menstrual age, 104 days; copulation age, 89 days. Doubtful case.
No. 894
(Dr. E. L. Mortimer, Baltimore, Md.)
Embryo, CR 121 mm.
White mother, age 29, three children and two abortions. Last period, July 24 to 28; criminal abortion, November 21. Husband works on a boat and returned home August 1.
Menstrual age, 120 days; copulation age, not over 112 days.
No. 142
(Dr. G. H. Hocking, Govans, Md.)
Embryo, CR 142 mm.
Mother, age 43, has five children. Menstruated May 29 to June 9; abortion, October 5 after several weeks' flow. Woman says pregnancy could not have taken place before June 18.
Menstrual age, 129 days; copulation age, 109 days. Doubtful case.
408 FRANKLIN P. MALL
The summary of these cases together with all others of the same kind which I have been able to gather from the literature, is given in table 1. This is an elaboration of the table given in the Manual. The data are sufficiently complete so that those who choose may look up the original records. Most of them, however, will be found in abstract form in the articles by Triepel and by Grosser.*^ The specimens in the Carnegie Collection are recorded above.
All of the specimens just given are entered upon figure 1. The mean menstrual age and the mean copulation age are taken from the data given in the table and in the curve published in the Manual. For the specimens here considered the menstrual ages are indicated by means of dots, the copulation ages by large solid circles. The time is calculated by days, and the measurements of the embryos are crown-rump. The numbers of several specimens for which the copulation age is given are marked in figure I; for instance, No. 443 and No. 1310. One of the Rabl cases is also indicated. I am of the opinion that all these marked records should really be excluded from the figure as they do not appear to be very reliable. However, I have included them for the sake of completion. Six of the copulation cases are crossed in the figure with an X, and are given again in table 2.
It will be noticed that these six records fall almost exactly upon the curve given. They are, I believe, the only ones which are entirely reliable; that is, they record embrj^os which are the product of single copulations, and for this reason their maximum ages are established. A word regarding specimen No. 26, which is recorded in the literature as representing an embryo 30 mm. long. As we are at present dealing with CR measurements, this should be 25 mm. It appears on the chart in the Manual as 30 mm., for the reason that the curve was constructed on the basis of the standing height, or CH length of the embryos. The tables given by Triepel and by Grosser should, therefore, have this measurement corrected accordingly.
I have also entered upon my figure the ages of the embryos
"Grosser, O. 1914 Alterbestimmung junger menschlichen Embryonen; Ovulations und Menstruationstermin. Anat. Anz., Bd. 47.
TABLE 1
LENGTH
OF EMBRYO
MENSTRUAL AGE
POSSIBLE TIME OF COPULATION IN DAYS BEFORE ABORTION
AUTHOR
m77i.
days
Embryc
0.15
38
Exactly 16 days
Bryce-Teacher, 1908
Ovum
5.5x3.3
42
20 days before and earlier
Reichert, 1873
Embiyf
1.0
22 and 30 days before
No. 1399
1.2 (?)
38
19 days (Delaporte)
See Grosser Anat. Anz. xlvii, 1914
1.3
34
Exactly 21 days
Eternod, Anat. Anz. XV, 1899
1.5(?)
35
14 days
Fetzer, Anat. Anz. Erg. Hft. xxxvii, 1910
2.75
44
17 days and later
No. 779
2.75
42
25 days and later
fWatt, Carnegie Conl tributions to Em
3.33
42
(Twin)
[ bryology, ii, 1915
3
46
26 days (?)
No. 1182b.
3.2
48
40 days and later
His, AME., vol. 2, 1882
4.0
35
25 days (?)
No. 470
4.0
50
38 days
No. 588
4.0
46
40 days and 17 days (?)
No. 1507
6.0
50
40 days and later
KoUmann's Atlas, 1907
■7
49
39 and 41 days
No. 208
7.75
57
45 days and later
His
8.8
42
Exactly 38 days
Tandler, Anat. Anz., xxi, 1907
9.8
28
27 days (?)
No. 1461
10
60
49 days and earlier
His
10.5
27
22 days (?)
No. 443
11
55
31 days (?)
Rahl, Entwickl d. Gesicht
13.6
63
53 days and later
His
14
65
Exactly 47 days
Rahl
14.5
65
46 days and later
No. 167
18
'54
Exactly 47 days
No. 1390
18
56
26 or 27 days (?)
No. 1584
25
75
Exactly 56 days
No. 26
26
65
56 days
No. 616
28
62
55 days (?)
No. 1535
31
69
57 days
No. 373
52.5
82
77 days (?)
No. 849
62
93
Not over 82 days
No. 591
70.5
95
75 or 87 days (?)
No. 1635
85(?)
95 days
No. 322
87
94
82 or 84 days (?)
No. 1295c
95
104
89 days (?)
No. 1310
121
120
Not over 112 days
No. 984
142
129
Not over 109 days
No. 1284
409
410
FRANKLIN P. MALL
according to their degree of development as given by Triepel in order to show that he has practically adopted the curve of development given by Bryce and Teacher and also by myself. He has really taken what I have designated as the copulation age, minus about two days for each stage, assuming, as do also
7p 80 90 |I00 I DAYS
2 3 4 5 6 7 e 9 10 II 12 13 14 15 WEEKS
Fig. 1 Menstruation age and copulation age taken from the curve constructed by me and published in the Manual of Human Embryology. All embryos are entered with CR length. I have also added for the sake of comparison the curve giving the convention of His. NL and CR give the neck-rump and crown-rump lengths respectively, according to His. The fertilization age is according to Bryce and Teacher for smaller embryos, and according to Triepel for larger ones. The dots record the menstrual age of the embryos under consideration, and the squares the copulation age. The crossed squares mark the best records, as mentioned in the text.
It may be noted again that the curves are not constructed from these records, but the records are entered to test the curve.
V AGE OF HUMAN EMBRYOS
411
TABLE 2
AtTTHOR
CR LENGTH OF EMBRYO
COPULATION AGE
Bryce and Teacher
771771.
0.15 1.3
8.8 14.0 18.0 25.0
days
16
Eternod
21
Tandler
38
Rabl, V
44
No. 1390
47
No. 26
56
Bryce and Teacher, that there is this interval of two days between copulation and fertihzation. For the sake of completion the curve giving the His convention is also included in the figure. I wish again to emphasize the fact that the curves given in the figure are not constructed from the records of the specimens in question, and it is quite clear, I think, that the new cases give no reason for materially altering the mean copulation curve as given by me in the Manual seven years ago. The relation of these curves to the ovulation age and to the fertilization age remains to be established, and as far as the evidence will permit this will be done in the following paragraphs.
OVULATION AGE
The question of the time of ovulation in relation, to menstruation or to copulation is by no means answered, although the literature upon the subject is extensive. If the time of ovulation could be definitely determined we would then be able to ascertain the ages of embryos with very fair precision. Wherever possible we have collected ovaries with our specimens, but so far have obtained only one accompanying a young ovum. This specimen, No. 97'0 in our collection, is from a Filipino girl, 16 years old, who died four days after taking hydrochloric acid with suicidal intent on account of her condition. The ovum, which measures 5x3 mm., is not quite normal in appearance but is well implanted. The corpus luteum is well formed, and solid, with no remnant of blood within it. The Herzog^ specimen, which
7 Herzog. 1909 A contribution to our knowledge of the earliest known stages of placentation and em^)ryonic development in man. Am. Jour. Anat., vol. 9.
412 FRANKLIN P. MALL ,
is also from a Filipino woman who was killed in an accident, likewise had a small o\iim measuring 2.3- x 1.2 mm., well implanted in the uterus. In this case the corpus luteum was 'fresh but closed.' The well known Reichert specimen which measured 5.5 X 3.3 mm., with a copulation age of 16 days or more, has in one ovary a well-formed corpus luteum, 20 x 17.5 mm. which has within it a small cavity containing some blood. Finally, Johnstone^ describes and pictures the corpus luteum of an ovum almost the size of Peters' specimen, which measures 13x10 mm. Its center is occupied by a large mass of pale, finely granular material which stained pink with eosin. The periphery is composed of a layer of lutein cells bordered on the inside by a layer of red blood corpuscles. The lutein layer, which is 8 x 10 cells deep, is crinkled, owing to papillary ingrowths of connective tissue. There is a great deal of vacuolation of the lutein cells and the whole layer is quite vascular. The specimen came from a woman, aged 29, who died suddenly, not having missed a period, nor was it suspected that she was pregnant.
A step in advance on the study of the structure of the corpus luteum was made by R. Meyer^ in his excellent pape"r on the subject. He classifies its development into four stages as follows :
1. Proliferation or early hyperemic stage of the Graafian follicle with transformation of the granular cells into lutein cells.
2. Early hyperemic stage of the corpus luteum with beginning transformation into the second stage of granular metamorphosis.
The blood-vessels now permeate the layer of lutein cells.
3. Mature or blossoming stage of the corpus luteum.
4. Stage of involution.
Sometimes when the follicle ruptures it simply collapses, and hemorrhage does not always take place within it. The specimens studied by Meyer were increased in number and reported
8 Johnstone, R. W. 1914 Contribution to the study of the early human ovum. Journal of Obstetrics and Gynaecology of the British Empire.
'Meyer, R. 1911 Ueber corpus luteum-Bildung beim Menschen. Archiv fiir Gynaekologie, Bd. 93, 1911.
AGE OF HUMAN EMBRYOS
413
in relation to the menstrual cycle by Ruge IP who gives the following data:
TABLE 3
STAGE
NUMBER OF SPECIMENS
TIME OF OCCURRENCE
IN RELATION
TO MENSTRUATION
Proliferation
10 10
44 18
1 to 14th day
Vascular
10 to 16th day
Mature
16 to 28th day
Involution
1 to 13th day
TABLE 4
STAGE
NUMBER OF SPECIMENS
TIME OF OCCURRENCE
IN RELATION
TO MENSTRUATION
Proliferation
10 10 44 18
1 to 14th day
Vascular
10 to 16th day
Mature
16 to 28th day
Involution
1 to 13th day
Ovulation occurred in the stage of proliferation, and always during the first 14 days of the period. However, this stage does not form a regular sequence of development during the first two weeks, but the specimens were of unequal development and could not be arranged in the order of time. It is impossible to determine the time elapsing between ovulation and the formation of the third stage of mature corpus luteum, but Meyer and Ruge believe that always a number of days must intervene. Finally, the stage of involution overlaps that of proliferation. At any rate the work of Meyer and Ruge demonstrates that the fresh corpus luteum as described by Fraenkel^^ appeared a number of days before he thought it did, thus completely overthrowing Triepel's assumption that the probable time of ovulation is on the 19th day. According to Ruge, it occurs sometime during the first 14 days of the menstrual month which supports the theory I am advocating.
These are all the reliable data I have been able to collect
10 Ruge II, Carl 1913 Ueber ovulation, corpus luteum and menstruation. Archiv fur Gynaekologie, Bd. 100.
11 Fraenkel: Archiv fiir Gynaekologie, Bd. 91.
THE AMERICAN JOURNAL OF ANATOMY, VOL. 23, NO 2
414
FRANKLIN P. MALL
regarding the time of development of the corpora lutea in human beings. I had thought that it would be possible to extend the subject somewhat further if the corpus hiteum in the pig could be standardized in relation to the size of the embryo found in the uterus. This work was carried through by Corner, but unfortunately does not include the earlier stages of the corpus luteum, and it is just these data that we need if we are to determine accurately the age of freshly ruptured Graafian vesicles. Corner^^ made a careful study of the histological changes in the corpus luteum of the sow for all but the earliest stages of pregnancy. He finds that the corpus luteum is already solid at 20 days, this stage being reached earlier, he believes, than in human beings where this central cavity remains longer. By the aid of refined cytological methods he recognizes seven distinct stages during pregnancy as follows:
TABLE
5
STAGES
LENGTH OF EMBRYOS
APPROXIMATE AGE
1. Preparatory period
Less than 20 mm. (I) 20-30 (II) 30-55 55-140 (I) 140-170 (II) 170-220 220-290
days
(?) 25
2. Exoplasmic development
25-30
3. Exoplasmic development
30-40
4. Transitorv period
40-75
5. Endoplasmic development
75-105
6. Endoplasmic development
105-110
7. Retrogression
110 to term
Although this study cannot be transferred to the human directly, it at any rate suggests that the latter may be standardized. It is hoped to establish at least a relation between the early stages of the corpus luteum and the size of the ovum and embryo; and that in the course of time the age of this body may be estimated with precision.
It may be noted that Corner showed definitely that the size of the embryo found in the uterus could be estimated with con 12 Corner, George W. 1915 The corpus luteum of pregnancy; as it is in swine. Contributions to Embryologj', vol. 2, Publication No. 223, Carnegie Institution of Washington.
AGE OF HUMAN EMBRYOS 415
siderable accuracy by the cytological condition of the lutein cells; however, all his specimens were from corpora lutea presumably a little older than the human ones mentioned above. In a measure we may fill in the gap in the earlier stages from the report by Sobotta^' on the development of the corpus luteum in the mouse. He found in this study that during the first 24 hours after ovulation the cavity of the follicle fills with serous fluid or blood, at the time the lutein cells become cut up into compartments by the formation of connective tissue septi. This process continues during the following day or two, and finally the central cavity is nearly obliterated, containing, however, a central mucoid nucleus at the middle of the third day after ovulation.
The irregular summary from the several species is about as follows: (1) In the mouse the central cavity of the corpus luteum is obliterated about the middle of the third day after ovulation; (2) it is obliterated in human specimens accompanying ova about the size of those studied by Bryce and Teacher, and by Peters; and (3), it is obliterated in the pig considerably before the 25th day. It may also be noted that Corner states that the corpus luteum of menstruation is of irregular shape in its development, while that of pregnancy is uniform and even. He speaks of the former as if the cells were arranged like a mob, and the latter as if organized like an army.
Finally, a few words regarding Fraenkel's studies, out of which Triepel has made so much capital. According to Fraenkel, Villemin in 39 operations found no freshly ruptured follicles in the first two weeks after the menstrual period, but observed many from 12 to 14 days before it. Fraenkel himself describes hemorrhagic follicles as follows: Very fresh, fresh, quite fresh and not very fresh, showing that his average of 19 days after the last menstrual period is not the average time of ovulation, but the average of older corpora lutea in several stages of development. From a study of Fraenkel's papers it may be seen quite clearly that what he reports as fresh corpora lutea are by no means
1^ Sobotta. 1896 Ueber die Bildung des corpus luteum bei der Maus. Archiv fiir Mik. Anat., Bd. 47.
416 FRANKLIN P. MALL
necessarily fresh, but may possibly vary in age fully a week. In fact he intimates that they are not all fresh, and Triepel makes a slight allowance for this reason. These papers have been carefully analyzed b}^ Grosser, who finally reached the • conclusion that ovulation does not take place on the 19th, but at the latest on the 16th day after the beginning of menstruation. This figure is not so very far from the average given in my curve; in fact it is a little more than the average age accepted by Triepel as the normal according to the degree of development of the embryo. Triepel has attempted to force a curve which runs exactly 12 days after the average menstrual age of specimens, into one which should be exactly 19 days after this curve, in order to fit Fraenkel's opinion regarding the proper time of ovulation. This of course is an impossible feat.
The conclusion to be drawn, therefore, is that we cannot possibly establish a satisfactory ovulation age of embryos from the data now at our disposal ; but I believe that we have material within our reach whereby we may eventually be able to determine with greater certainty the probable time of ovulation. Before this can be done with the human, however, it will be necessary to study anew the degree of development of the corpus luteum for various days after menstruation, with new material selected from cases which are otherwise normal. This can be done in any large gynecological clinic.
FERTILIZATION AGE
According to Bryce and Teacher, the comparative infrequency of pregnancy during continuous cohabitation points to some special circumstance connected with successful impregnation. This circumstance would appear to be simultaneous ovulation and limited power of fertilization on the part of the spermatozoa. As regards the former the work of J. G. Clark is of interest. According to this writer ovulation is accompanied with hyperemia of the ovary, and, he believes, is hastened by it. He injected the blood vessels of an ovary in which there were fresh corpora lutea, as well as swollen Graafian follicles, and found that
AGE OF HUMAN EMBRYOS 417
the injected fluid immediately ran out of the ruptured follicle. In a few instances the fluid entered mature follicles, causing them to become dense and finally to rupture when the vascular pressure was continued for a sufficiently long period. This suggests at least that a factor in fertilization is the rupture of a Graafian vesicle, due to orgastic reaction in the uterus, tubes and ovaries when copulation takes place immediately after menstruation. At this time ovulation is most likely to occur in tower animals, and all the facts indicate that the same is true in human beings. It is known that in the rabbit, dog and pig there must be repeated copulation in order to insure impregnation. A single mating rarely suffices. Thus, for instance, according to Weysse,i^ only three out of the nine sows became pregnant after being covered but a single time. This would indicate that the fertilization power of the sperm was of short duration, as Bryce and Teacher seem to think is the case in human beings.
According to Waldeyer^^ live spermatozoa were found in the bitch eight days after copulation, and dead cells, that is motionless cells at the end of 17 days. Living moving spermatozoa were found in a woman three days after death. Living sperm cells were found in the Fallopian tube of a patient 9 days after admission to the hospital and 3^ weeks after copulation. On the other hand, spermatozoa have been found upon the surface of the ovary of the rabbit and sow two hours after copulation. In Waldeyer's opinion the power to fertilize remains as long as the sperm cells retain normal motility, and there are no facts to deny that human sperm has the power to fertilize over a week after copulation.
Spermatic cells of animals that emit them into water die in a very short time if they are greatly diluted, and have a much longer life if only a little water is added. Thus in fertilizing trout eggs 'dry' sperm is used, while if the sperm is added to water containing the eggs but few eggs are fertilized. This
1^ Weysse, Arthur Wisswald 1894 The bhistodermic vesicle sus scrofa domesticus. Proc. Amer. Acad. Arts and Sciences, vol. 30.
1^ Waldeyer, W. 1906 Hertwig's Handbuch der Vergleich. und Exper. Entwickelungslehre der Wirbeltiere. Bd. 1, Tl. 1, Erste Halfte.
418 FRANKLIN P. MALL
question has been tested recently in Arbacia by F. R. Lillie,i^ who makes the following interesting statements: The spermatozoa are absolutely immobile while they are in the body of the male, but become intensely active when suspended in sea-water. They then become relatively inactive, but can be restored again by the addition of fresh sea-water. When greatly diluted they lose their fertilizing power completely in about an hour, and when diluted by 250,000 times their volume in water this power lasts but a few minutes. The loss of fertilizing power cannot be due to a loss of motility, for long after the former occurs no loss of vitality or motion is observed. In man the secretion of the prostate gland maintains the motility of spermatozoa much more effectively than does normal saline solution, and it is said that the secretions of the mucous membrane of the uterus and tubes have a similar influence. Thus it would seem that when motility is accelerated it does not indicate that the power to fertilize is prolonged, as asserted by Waldeyer. Lillie's experiments certainly do not favor such a view, and Bryce and Teacher infer the same when they state that were the spermatozoa to retain for a long time their power of fertilization, no ovum could escape fertilization.
For the sake of argument Bryce and Teacher deduct 24 hours from the copulation age of their specimen (16^ days) .and estimate that it would have been 15| days old had it lived up to the time of abortion. This seems to me to be reasonable, as are the other statements in their admirable paper.
In view of the difference between the fertilization power of spermatozoa and their motility, as expressed in Lillie's report, we may admit with considerable safety that the fertilization power of sperm is of shorter duration than is the power on the part of the egg to be fertilized. Furthermore, the theory that a fruitful copulation should be accompanied by ovulation at about the same time is a necessary one, in order to account for all of the combinations which are encountered in human beings. Nor is the assumption of Bryce and Teacher of an oestrus following
1^ Lillie, F. R. 1915 Analysis of variation in the fertilizing power of sperm suspensions of Arbacia. Biol. Bull., vol. 28.
AGE OF HUMAN EMBRYOS
419
menstruation untenable, and the possibility of a relation between orgastic reaction and ovulation is not to be overlooked.
An interesting study in this connection has been made by Siegel," using the wives of German soldiers as his subjects. These women, who became pregnant during their husband's furlough, came to the maternity hospital to be confined, and
DAYS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 lb 17 18 19 20 21 22 23 24 25 26 27 28
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n
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n
n
80
ME
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"ION
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TRL
UM
iNTERMENSTRUUM
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RAE
MENSTF
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70
60
DVU
LA"
ION
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,
50
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40
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Fig. 2 Cohabitation curve according to Siegel. The main division of the menstrual month and the probable time of ovulation are given. One hundred cases of pregnancy, occurring in the wives of soldiers after their husbands' furlough of one week. Each day of the furlough is entered as a possible day of conception. In all probability the 1st to the 4th day and the 18th to the 21st day belong to the sterile portion of the month.
it was easy to obtain records of the menstrual history as well as the times of furlough, which in each case was of about a week's duration. Figure 2, taken from Siegel's paper, gives the result of the tabulation of 100 of such cases. Each day of the furlough is entered in the curve. Thus, if the furlough lasted from the
17 Siegel, P. W. Woch., 41.
1915 Warum ist der Beischlaf befruchtend? Deut. Med.
420 FEANKLIN P. MALL
8th to 16th day of the menstrual cycle it was entered for each of these days.
It is noteworthy that there was no entry for the last seven days of the menstrual month, indicating that pregnancy did not take place either a week before this nor within the week following ; that is, there is a sterile period of about 18 days and a fertile period from the end of menstruation to the 15th day, which includes the probable time of ovulation. Of course only those cases which came to the maternity hospital could be recorded, and it is interesting to note that none of the 100 pregnancies dated from a furlough during the last week of the menstrual month. Such did not end in conception. Siegel was able to gather 10 cases in which the husband was on furlough a few days before the menstrual period, and in none did pregnancy follow. He cites further cases gathered by Wohler from the records of the same maternity hospital for the past ten years. These included 160 pregnancies among newly married women, in whom conception had occurred during the first five weeks after marriage. Among this group there were 65 cases in which marriage took place within the eight days preceding the menstrual period, and in each of them one more menstruation followed, which fact alone would indicate a sterile condition during the week preceding it. The records of Siegel, although not entirely satisfactory, demonstrate quite conclusively that the most probable time for conception is during the week or ten days after the period of menstruation.
From what has been written above we may, for the sake of argument, accept one day as the average time between copulation and fertilization. The time at which this is most likely to occur is between the 4th and 13th day after the first day of menstruation, as shown by the following table. This table is compiled from the records of our own cases, given above, each datum being obtained by subtracting the copulation age from the menstruation age. A similar result is obtained by dividing the total number of days by the number of cases, which equals exactly 13. That is, the average copulation date is the 13tli day after the beginning of the last menstrual period. The figures upon which this result are
AGE OF HUMAN EMBRYOS
421
based are not altogether satisfactory, but if the six cases given in the table are recorded, the average date is one day later; that is, the 14th. The figures of these cases are as follows:
TABLE 6
Days between menstruation and copulation
No. of cases.. . .
2122 1 2
23
2425
l|
2830 1 1
TABLE 7
AUTHOR
LENGTH OF EMBRYO
TIME BETWEEN FIRST DAY OF MENSTRUATION AND COPULATION
Bryce and Teacher
tnm,
0.15
1.3
8.8
14.0
18.0
25.0
days
22
Eternod
13
Tandler
4
Rabl
18
No. 1390
7
No. 26
.
19
In this group just half of the cases date from the first two weeks of the menstrual cycle, and the other half from the second two weeks. It is recalled that in over 1000 cases of full term births the mean as computed from the time of menstration and of copulation duration of pregnancy differed exactly 1 1 days, and that in my curve a difference of 10 days was taken. The theory of Bryce and Teacher and of Triepel is that fertilization takes place two days after copulation, and, therefore, they figure two days less than I did as the mean ovulation or fertilization age. Between these two theories I presume that we are within two or three days of the real age.
It appears to me probable that fertilization takes place nearly always within the uterine tubes — very rarely upon the surface of the ovary, as ovarian pregnancy is extremely rare; and probably also because the spermatozoa have lost their fertilizing power by the time they have passed the tube. No doubt this power is greatest in the tubes, as in these narrow channels the sperm would
422
FRANKLIN P. MALL
not be unduly diluted, but instead there would be a tendency to bring it together again. The ovum would probably be fertilizable for fully 24 hours after o\nilation, this time being sufficient to bring it into the outer end of the tube. The following table gives the copulation age of the rat's ovum, according to Huber, and of the dog's, according to Bischoff. I have taken the measurements from their illustrations which are to scale. The third column gives the greatest diameter of the human ovum, with the length of the embryo in the 4th column. The second portion of the table gives the fertilization age for the third week, according to Bryce and Teacher and to Triepel. It will be seen that the former allows 48 hours for fertilization after copulation, a period of time which, in my opinion, is abundantly long. Finally Triepel's column is practically identical with that of Bryce and Teacher.
TABLE 8
COPULATION AGE
FERTILIZATION AGE
Age
Rat (Huber)
Dog
(Bischoff)
Human Ovum
Embryo
Embryo
(Bryce and
Teacher)
Age (Triepe!)
days 1
2 3 4 5 6 7 8 9
10 11 12 13 14 15 16 17 18 19 20 21
■mm.
' 0.07 0.07 0.09 0.10 0.11 0.25 0.40 0.65 1.30
mm.
0.15 0.14 0.14 0.16 0.16 0.18 0.20 0.21 0.28 0.30 1.00 2.00 3.00 4.00 5.00 5.00 G.OO
mm.
2.0 3.5 5.0 6.5 8.0 10.0
m7n.
0.15
0.2
0.3
0.6
0.9
1.3
mm.
0.15 0.19
0.37
1.3
1.54
mm.
0.15 0.19
0.37
1.3
1.54
2.15
