. The physiology of reproduction. Reproduction. FCETAL NUTRITION: THE PLACENTA 395 (Fig. 87), radiating from small circular spots, twenty or thirty to the square inch, which represent the gland-mouths (Turner ^). It is usually stated that the uterine surface epithehum remains intact; but Assheton has recently proved that it shows signs of degeneration as early as the eighth day, and at the eighteenth day is reduced to a thin layer. Three days later, however, it again appears normal and is formed of long columnar ceUs, to the ends of which the trophoblast fits closely, sending proto- Blv mes—\.
. The physiology of reproduction. Reproduction. FCETAL NUTRITION: THE PLACENTA 395 (Fig. 87), radiating from small circular spots, twenty or thirty to the square inch, which represent the gland-mouths (Turner ^). It is usually stated that the uterine surface epithehum remains intact; but Assheton has recently proved that it shows signs of degeneration as early as the eighth day, and at the eighteenth day is reduced to a thin layer. Three days later, however, it again appears normal and is formed of long columnar ceUs, to the ends of which the trophoblast fits closely, sending proto- Blv mes—\. Fig. 88.—Section through the wall of the uterus and the blastocyst of the pig at the twentieth day of pregnancy (Assheton). mes, mesoblast; , foetal vessel; Tr, trophoblast; Ep, long columnar epithelium of uterine surface. plasmic processes between the cells (Fig. 88). These processes may even reach past the epithehum to the underlying layer of dilated capillaries (Robinson), and absorb nutritive material or effect gaseous exchanges. The trophoblast is single-layered throughout, and, after the first three weeks, forms a syncytium. Internally to it Kes the mesoblast, which in the main follows its ridges and furrows, but occasionally bridges across a fold. It is vascularised by the vessels of the aUantois, which completely surrounds the embryo. The gland-mouths he along the course of the vessels (Assheton). No formation of viUi takes place, and the attachment never ' Turner, Lectures on the Comparative Anatomy of the Placenta, Edinburgh, 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
