193 



Fig. 5. A strip through the middle of a placenta of about fourteen days. 

 The allantoic villi have grown still further into the trophoblast. In 



the glycogenic portion of the trophoblast two large sinuses are shewn. 

 Above this is, firstly, the disintegrating maternal glycogenic tissue, 

 bounded outside by the flattened cells; and, secondly, the thickening 

 of connective tissue, in the cells of which glycogenesis has already 

 begun, at the root of the mesoraetrium. 



Fig. 6. A strip through the middle of the placenta shown in Fig. 11. 



The allantoic portion is now very considerably broader than be- 

 fore. The embryonic capillaries in which, at this stage, both nu- 

 cleated and non-nucleated corpuscles are found, are much more 

 numerous. 



The glycogenic portion has become enormously thick, partly by 

 the distension of its cells with glycogen, partly by continued growth 

 in the lower layers; in the processes -which dip down from this 

 region into the allantoic portion glycogenesis has now set in. 

 In its upper part this glycogenic tissue is seen to be traversed by 

 a large blood sinus; while again above this it has encroached upon 

 the space occupied in the earlier stages by the similar tissue of 

 maternal origin; in doing so it has engulfed degenerating ma- 

 ternal cells, and maternal, arterial, blood vessels. Two of the latter, 

 lined by a proper endothelium and surrounded by a proper wall 

 are shown in the figure. 



External to this embryonic glycogenic tissue are a few elongated 

 supporting cells, amongst which may be seen the remains of the 

 maternal glycogen cells. These are bounded outside by the layer 

 of flattened connective-tissue cells, outside which again is the mass 

 of glycogen cells at the root of the mesometrium. 



Fig. 7. Transverse section of the uterus on the fifth or sixth day, before 

 the embryo has become fixed. The embryo may be seen on the 

 anti-mesometric side of the uterine lumen. 



Fig. 8. Transverse section of the uterus on the seventh day shortly after 

 fixation of the embryo. The proliferation of subepithelial tissue on 

 the anti-mesometric side (omphaloidean region) is well-marked. 

 Near the muscularis the fundi of the glands may be seen. Com- 

 pare Fig. 2. 



Fig. 9. Transverse section of the uterus on about the ninth day. 



In the embryo the amniotic and intra-trophoblastic cavities are 

 completely separated ; the allantoidean trophoblast is much enlarged, 

 and lacunae, in which maternal blood is circulating, are formed 

 in it. In the uterus the blood vessels are still more dilated, and 

 the lumen still persists. 



Fig. 10. Transverse section of the uterus on about the twelfth or thir- 

 teenth day. 



In the embryo the attachment of the blood vessels of the allan- 

 tois and area vasculosa to the phcental trophoblast and yolk-sac 

 respectively may be seen. 



