CHANCiES IN FETAL VESSELS OF THE LIVER 



519 



disappearance after beeoiuiiig detached is probably due to the 

 presence of degeneration and absorption similar to that which 

 occurs in the umbilical vein in the dog and sheep. It is also 

 interesting that no proliferation of the endothelium was noticed 

 and that the musculature was comparatively well-preserved so 

 long after the vessels were of any functional value to the organism. 

 In some cases (fig. 12) the endothelium had been cast off, however, 

 and plugged the small lumen. The cells which had undergone 

 degenerative changes were not infrequently quite clearly out- 

 lined, somewhat stellate and formed a meshwork bv the union of 





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Fig. 26 Omphalomesenteric vessel from a pup 91 hours old. The arrange- 

 ment of the inner portion of the wall suggests that of the original vessel. The 

 lumen contains well-preserved erythrocytes. The outer lighter portion is com- 

 posed of very loose fibrous connective tissue. The endothelium is intact in this 

 portion. X275. 



their processes. In other cases the lumen which contained 

 well-preserved erythrocytes, and the bounding endothelium 

 was well-preserved but the musculature had become so degener- 

 ated that it was difficult to recognize it as such. It had become 

 syncytial and had lost its distinctive staining qualities besides 

 be ng markedly vascularized at the periphery where it was 

 partly or wholly replaced by connective tissue. Similar de- 

 generative changes were also observed in the intima. 



