. The physiology of reproduction. Reproduction. FCETAL NUTRITION: THE PLACENTA 443 nest remaining which formed the placenta. After a long interval this was proved to be wrong by Reichert ^ and Hensen.^ The fertilised ovum reaches the uterus as a morula or early blastocyst, surrounded by the zona radiata. On the seventh day the zona disappears and embedding begins, but even before this, according to von Spee,^ the ovum is fixed by processes which extend from the cells of the implantation pole through the zona and come into direct metabolic relationship with the epithehal ceUs. As in the mouse,
. The physiology of reproduction. Reproduction. FCETAL NUTRITION: THE PLACENTA 443 nest remaining which formed the placenta. After a long interval this was proved to be wrong by Reichert ^ and Hensen.^ The fertilised ovum reaches the uterus as a morula or early blastocyst, surrounded by the zona radiata. On the seventh day the zona disappears and embedding begins, but even before this, according to von Spee,^ the ovum is fixed by processes which extend from the cells of the implantation pole through the zona and come into direct metabolic relationship with the epithehal ceUs. As in the mouse, the blastocyst remains small. mes. Fig. 107.—Longitudinal section of the uterus and implantation cavity of the guinea-pig. (From Duval's "Le Placenta des Rongeurs,'' Journ. de I'Anat. etde la Phys., 1892.) mes, mesometrial border ; gl, uterine glands ; I, uterine lumen ; bl, blastodermic vesicle. about one-tenth of a miDimetre in diameter. At its point of contact with the mucosa, the epitheUum is rapidly eroded, and absorbed along with its fat globules by the foetal ectoderm. At the same time changes occur in the deeper layers. In the non- pregnant uterus two layers are present, a sub-epitheUal layer of embryonic connective tissue cells interrupted only by capillaries and glands, and a deeper, more reticulate layer. Before the ninth day of pregnancy, no very marked changes occur in the ' Reichert, "Beitrage zur Entvi^icklungsgeschichte des Meerschweinchens," Abhandl. d. Akad. d. Wiasensch. zu Berlin, 1861. ^ Hensen, " Beobachtungen iiber die Befruchtung und Entwicklung des Kaninchens und Meerschweinchens," Zeit. f. Anat. u. Entwick., vol. i., 1866. ' Von Spec, " Die Implantation des Meerschweincheneies in die Uterus- wand," Zeit. /. Morpkol. u. Anthropol., vol. iii., Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrati
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