. The physiology of reproduction. Reproduction. FCETAL NUTRITION: THE PLACENTA 391 sac or omphaloidean placenta reaches its full development at the time when the allantois comes in contact with the tropho- blast (see p. 451). Then the yolk-sac is gradually separated from the wall, more and more of its viUi being peeled out from the trophoblast as the separation increases. The vitelhne circulation at the same time diminishes, though it never ceases entirely (Hubrecht ^). AUantoidean region of trophosplierc Ornphaloidean region of tropkospliere. Decidua reflexa Uterine luinen - Mesometi'ium Fie.
. The physiology of reproduction. Reproduction. FCETAL NUTRITION: THE PLACENTA 391 sac or omphaloidean placenta reaches its full development at the time when the allantois comes in contact with the tropho- blast (see p. 451). Then the yolk-sac is gradually separated from the wall, more and more of its viUi being peeled out from the trophoblast as the separation increases. The vitelhne circulation at the same time diminishes, though it never ceases entirely (Hubrecht ^). AUantoidean region of trophosplierc Ornphaloidean region of tropkospliere. Decidua reflexa Uterine luinen - Mesometi'ium Fie. 85.—Diagram to lUastrate the fcetal membranes of Erinaceus. (From Hubrecht's " The Placentation of Erinaceus europcms," Quar. Jour. Micr. Scl, vol. XXX., 1889.) In the shrew, the yolk-sac adheres by a zonary strip to lateral cushions of proliferated mucosa, but the resulting yolk- sac placenta is avillous (Hubrecht ^). The trophoblast is again thickened, and in its spaces maternal blood appears, but at a later date than in the hedgehog. The maternal blood is bodily ' Hubrecht, " The Placentation of Erinaceus europceus," Quar. Jour. Micr. Set., vol. xxx., 1889. " Hubrecht, " The Placentation of the Shrew," Quar. Jour, Micr. Sci., vol. XXXV., Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marshall, F. H. A. (Francis Hugh Adam), 1878-1949; Cramer, William, 1878-1945; Lochhead, James. London, New York, Longmans, Green
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectreproduction, bookyea
