147 



in glycogenic trophoblast (Fig. 29, 30). A careful comparison of 

 closely succeediug stages suggests that one, at least, of the causes 

 to whicb this disintegratiou is due is the enlargenient of the space 

 occupied by this tissue unaccompanied by a corresponding growth 

 by cell division on the part of the tissue itself. 



A further and very curious phenomenon, which may be ob- 

 served at this time, but of which I am sorry to say I do not 

 in the very least comprehend the significance, is the intrusion of 

 these glycogen cells into the maternal blood vessels (Fig. 2). The 

 thin walls of these vessels may be seen in places to be breaking 

 down, and giving passage to the glycogen cells which, once in 

 the arterial stream, become transported to all parts of the pla- 

 centa. They are found in the trophoblastic sinuses and lacunae, 

 and, wherever found, their very definite characters enable them 

 to be instantly recognised (Fig. 29). In the sections these cells 

 appear to be actually forcibly making their way into the blood 

 vessels ; and the fact that the actual intrusion is only to be observed 

 at a stage when the subepithelial tissue is still closely packed, 

 suggests that the process may merely be a result of a pressure 

 exerted upon the walls by the crowded cells outside. 



Simultaneously with the intrusion of the glycogen cells a few 

 blood corpuscles appear to be extruded from the vessels; at least 

 blood corpuscles may occasionally be found lying about among 

 the separated glycogen and supporting cells. At the same time it 

 may be possible that these corpuscles have not emerged from the 

 larger vessels, but are set free by the complete breaking up of 

 the minufce capillaries which at au earlier stage formed every- 

 where an anastomosing system. At the root of the mesometrium 

 is a mass of tissue separated from the cells we have been con- 

 sidering by the layer of elongated connective tissue cells; it com- 

 mences about this time, to undergo a precisely similar transform- 

 ation into rounded glycogen cells, and later on it will break up 

 in exactly the same manner. 



The connective tissue layer just mentioned is not to be con- 

 fused with the muscularis. The smooth muscle fibres of the cir- 



