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Fig. 4. Section through the germinal disc of the ripe ovarian ovum of a fowl while yet enclosed in its capsule

a. Connective-tissue capsule of the ovum.

b. follicular epithelium, at the surface of which nearest the ovum lies the vitelline membrane,

c. granular material of the germinal disc, which becomes converted into the blastoderm. (This is not very well represented in the woodcut. In sections which have been hardened in chromic acid it consists of fine granules.)

w.y, white yolk, which passes insensibly into the fine granular material of the disc.

x, germinal vesicle enclosed in a distinct membrane, but shrivelled up by the action of the chromic acid,

y, space originally completely filled up by the germinal vesicle, before the latter was shrivelled up by the action of the chromic acid.

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Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, 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 terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)

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