. Comparative embryology of the vertebrates; with 2057 drawings and photos. grouped as 380 illus. Vertebrates -- Embryology; Comparative embryology. 924 CARE AND NOURISHMENT OF THE DEVELOPING YOUNG and seventh days of uterine existence (, 9 and 10 days after copulation) (fig. 145I-L). The blastocyst eventually forms a much elongated attenuated structure about 1 meter long. During the earlier portion of the free uterine period the many blastocysts of the ordinary conceptual process in the sow become spaced within the horn of each uterus, an intriguing process which continues to remain baffl
. Comparative embryology of the vertebrates; with 2057 drawings and photos. grouped as 380 illus. Vertebrates -- Embryology; Comparative embryology. 924 CARE AND NOURISHMENT OF THE DEVELOPING YOUNG and seventh days of uterine existence (, 9 and 10 days after copulation) (fig. 145I-L). The blastocyst eventually forms a much elongated attenuated structure about 1 meter long. During the earlier portion of the free uterine period the many blastocysts of the ordinary conceptual process in the sow become spaced within the horn of each uterus, an intriguing process which continues to remain baffling. From 10 to 13 days after copulation the blasto- cysts experience the gastrulation processes (see figure 145M-R; and figures 208 and 209); from days 13 to 15 body form is developed gradually (fig. 242A-F) and the amnion and chorion are formed (fig. 242G). From days 14 to 17 the allantoic diverticulum grows rapidly (figs. 242G; 370C-D). At this time the chorionic vesicle as a whole shortens and becomes much larger in transverse section. The yolk sac of the embryo of 16 to 17 days is greatly enlarged in relation to the size of the embryo, and the entoderm at its distal end lies closely apposed against the chorionic ectoderm (figs. 242F; 370C). As the allantoic cavity expands, the yolk sac, relatively speak- ing, contracts, and a relationship is established similar to that in figure 370D. As the allantois expands its mesoderm comes in contact with the mesoderm of the chorionic membrane and fuses with it (fig. 370E). This new layer forms the chorio-allantoic membrane. The chorio-allantoic membrane becomes folded into elongated folds which fit into similar folds of the uterine mucosa. A relationship thereby is formed as shown in figure 373B. COTYLEDONS. DOG, CAT, SEAL, GENET Fig. 378. External appearance of chorionic vesicles in various mammals. (A) Pig. This placental type is called diffuse. (A') Enlarged drawing of small cotyledon or areola. (B) Cow. Observe large cotyledons.
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