File:Foster034.jpg

FIG. 34. TRANSVERSE SECTION THROUGH THE DORSAL REGION OF AN EMBRYO OF 45 HOURS.

A. epiblast. B. mesoblast. C. hypoblast consisting of a single row of flattened cells. M. c. medullary canal. P. v. mesoblastic somite. W. d. Wolffian duct. S. o. Somatopleure. S.p. Splanchnopleure. p.p. pleuroperitoneal cavity, c. h. notochord. a. o. dorsal aorta, v. blood-vessels of the yolksac, o.p. line of junction between opaque and pellucid areas ; w. palisade-like yolk spheres which constitute the germinal wall.

Only one-half of the section is represented in the figure if completed it would be bilaterally symmetrical about the line of the medullary canal.

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Reference

Foster, M., Balfour, F. M., Sedgwick, A., & Heape, W. (1883). The Elements of Embryology. (2nd ed.). London: Macmillan and Co.

The Elements of Embryology (1883)

Volume 1 The History of the Chick: Egg structure and incubation beginning | Summary whole incubation | First day | Second day - first half | Second day - second half | Third day | Fourth day | Fifth day | Sixth day to incubation end

Volume 2 The History of the Mammalian Embryo: General Development | Embryonic Membranes and Yolk-Sac | Organs from Epiblast | Organs from Mesoblast | Alimentary Canal | Appendix