OCR Text |
Show 1 9 0 5 .] PLACENTA OF THE SPINY MOUSE. 2 8 3 ami containing dead nuclei, which I must regard as cell-detritus. rhis layer probably lay against, and was no doubt more or less attached to, the uterine wall (text-fig. 45, D). Text-fig. 43. A section of a portion of the placenta of Acomys taken vertically near the centre of the organ, where the foetal capillaries are forming a network round about the channels containing maternal blood. F.BV. Foetal capillary. LE. Maternal leucocyte. MCH. Maternal blood in channels excavated in the trophoblast of the foetus. T. Trophoblast nuclei. X 480. From this point and passing over the edge of the placenta, and covering the free surface of the foetal side of the placenta, a flattened attenuated epithelium can be distinguished (text-fig. 45, H, p. 285). This becomes thicker and more cubical as it nears the point at which the yolk-sac wall is connected with the placenta, and here it passes into the decidedly cubical or columnar epithelium of the yolk-sac. This layer continued in the other direction woidd pass at some period into the distal wall of the yolk-sac, though whether this distal wall exists at the period under examination I cannot say. The rough surface of vascular attachment, so far as 1 can judge from the general character of the cells, is composed entirely of maternal tissue. This tissue is of that kind so frequently found where trophoblastic ingrowth is about to take place, and had been named by Hubrecht trophospongia (text-fig. 44, p. 284). Text-fig. 45 is a diagrammatic representation of a section passing through the centre of the placenta. The placenta, as |