192 



round the linnen of the uterus itselt', may be seen the formeny 

 vacuokited but now flattened cells. 



At the very top of the figure is a layer of flattened cells irame- 

 diately subjacent to the muscularis. Below proliferation of the (allan- 

 toidean) subepithelial tissue has already begun; small blood vessels 

 are also to be seen. 



Lower down, to botb sides of the embryonic pit, the tissue resem- 

 bles rather that found on the anti-mesometric side. the cells being 

 larger and the blood vessels dilated. 



Below this is seen the proliferated subepithelial tissue of the anti- 

 mesometric or omphaloidean region, containing small blood vessels, 

 and the long drawn out necks of the glands; and, at the bottom 

 of the figure the loose, somewhat flattened connective tissue next 

 the muscularis. 



Fig. 2. A strip through the mesometric side of the uterus at a somewhat 

 later stage (about the eighth day). The degeneration of the epithe- 

 lium is much more advanced, and the lumen is occupied by débris, 

 red blood corpuscles extravasated from the neighbouring blood 

 vessels, and leucocytes. The allantoidean trophoblast, the formation 

 of which had only just commenced in the previous stage, is now 

 of a considerable size: lacunae are excavated in it. To the right 

 and left are dilated venous sinuses. 



Above is the proliferated subepithelial (later glycogenic) tissue of 

 the allantoidean region, containing numerous small, arterial blood 

 vessels. 



Fig. 3. A similar strip from the uterus figured in Fig. 9. 



The allantoidean trophoblast, which is bounded below by the somato- 

 pleure, is still further enlarged ; it contains lacunae filled with 

 maternal blood. 



The sides of the uterine lumen, into which the trophoblast has 

 advanced, are beginning to be pushed apart, but the layer of flat- 

 tened cells here separating maternal from embryonic tissues is still 

 evident. 



The proliferation of subepithelial tissue has continued (mitoses are 

 still found at this stage) and the formation of glycogen in the cells 

 has just begun. 

 The blood vessels are much larger than in the previous stage. 



Fig. 4. A similar strip from the section shown in Fig. 10. 



The allantoic vilü are commencing to grow into the trophoblast. 

 Glycogenic vacuolation has now appeared in the layer of tropho- 

 blast immediately adjacent to the subepithelial tissue. 

 The disintegration of the maternal glycogenic tissue is well advan- 

 ced; many of the glycogen cells have been intruded into the blood 

 vessels. 



The latter are much dilated. 



Outside the layer of flattened connective-tissue eells is the thickening 

 of tissue at the root of the mesometrium. 



