. The physiology of reproduction. Reproduction. 396 THE PHYSIOLOGY OF REPRODUCTION goes beyond the stage of apposition except for the proto- plasmic extensions of the trophoblast (Kg. 89). The uterine mucosa contains no special cotyledonary areas such as are found in the sheep and cow. The surface epithehum, though it shows the degenerative changes already referred to, is apparently never completely destroyed. The glandular epithehum does not at any time show signs of de- generation. It secretes actively during the early stages, and probably during the whole of pregnancy. As in the sheep and o
. The physiology of reproduction. Reproduction. 396 THE PHYSIOLOGY OF REPRODUCTION goes beyond the stage of apposition except for the proto- plasmic extensions of the trophoblast (Kg. 89). The uterine mucosa contains no special cotyledonary areas such as are found in the sheep and cow. The surface epithehum, though it shows the degenerative changes already referred to, is apparently never completely destroyed. The glandular epithehum does not at any time show signs of de- generation. It secretes actively during the early stages, and probably during the whole of pregnancy. As in the sheep and one of the lemurs (Galago agisymbanus), the glandular orifices. 6W MB Fig. 89.—Diagram representing a stage in the formation of the placenta of the pig. (From Robinson, "Hunterian Lectures," Jour. Anal, and Phys,, vol. xxxviii., 1904.) UM, uterine muscle; MB, maternal blood-vessel ; UG, uterine glands; UB, uterine epithelium ; FB, foetal ectoderm ; FM, foetal mesoderm. are covered by domes of trophoblastic cells, which absorb the secretion and transmit it as nutriment for the developing embryo by the allantoic vessels. The sub-epithehal tissue is gelatinous, and early in pregnancy it begins to increase in thickness by a widening of the lymphatics and blood-vessels and a new formation of capillaries. The constituents of the nutriment provided for the embryos are referred to later (see p. 400). Mare.—In the mare the details of placental development are not yet known. In the early stages the blastodermic vesicle is attached to the uterine mucosa by the trophoblast covering the lower pole of the ovum, and the attachment is aided by the formation of dehcate, nearly parallel ridges (Bwart ^). Vilh are ' Ewart, Critical Period in the Devdopment of the Horse, London, 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 t
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