File:Bailey047.jpg

Fig. 47. Transverse sections of blastoderm of chick (21 hours' incubation).

Hertwig.

a, Section through primitive groove, posterior to Hensen's node.

b, Section through Hensen's node.

"A transverse section through the primitive pit shows essentially the same structural arrangement as in the streak farther caudally (Fig. 47, B). In some birds the pit opens into the archenteron, but not in the chick. The region of the primitive knot also shows the same arrangement, the knot itself being an elevation just in front of the pit. Caudally the primitive groove becomes more shallow and finally disappears, the caudal end of the streak broadening out as the primitive plate."

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Pages where the terms "Historic Textbook" and "Historic Embryology" appear on this site, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the interpretation of developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these interpretations may not reflect our current scientific understanding. (More? Embryology History)

Reference

Bailey, F.R. and Miller, A.M. (1921). Text-Book of Embryology. New York: William Wood and Co.

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