504 ARTHUR WILLIAM MEYER 



other case and it is also evident that both processes of obUter- 

 ation may be present at the same time. 



From the facts observed especially in the umbihcal veins of the 

 dog and sheep, it is apparent that similar processes are initiated 

 in them but that they cannot extend beyond the initial stage be- 

 cause of the rapid degeneration and absorption of these vessels. 

 In the cat, rabbit and guinea-pig, on the other hand, in which the 

 disappearance of the umbil cal veins is a much slower process 

 a corresponding and complete fibrous transformation may take 

 place. 



So far as the umbilical vein and hypogastric arteries of these 

 animals are concerned no evidence whatever for the origin of 

 connective tissue from endothelium has been obtained. Merkel 

 a'so ('03) insists that the endothelial cells do not take part in 

 the organization of a thrombus, and asserts that Baumgarten was 

 mistaken when he concluded that an actual proliferation of the 

 endothelial cells takes place. Nevertheless, in the absence of 

 corroborative facts it is not denied that Haberda was mistaken 

 when he declared that in man "Die our Obliteration der Nabel- 

 gefasse fiihrenden Veranderungen bestehen in einer zu Binde- 

 gewebesich metamorphosierenden Wucherung desGefassendothels 

 der sich an den Nabelenden der Gefasse eine von der Nabelwunde 

 ausgehende entziindliche Zelleninfiltration hinzugesellt." This 

 proLferation which is said to take its origin from the endothelium 

 of the obliterating vessels was described by Thoma, confirmed 

 by Baumgarten, emphasized by Hauptmann and in a measure 

 corroborates the observations of Mall ('02 and '12) and of Kling 

 ('02) to the effect that reticulums may arise from endothelium. 



A very interesting phenomenon was noticed in the extra- 

 abdominal portion of an umbilical vein of a lamb which died 

 during labor. In the case of this lamb a portion of the vein 

 contained blood which was in process of coagulation. Upon 

 microscopical examination the lumen which was fairly regular 

 save for small ridges was seen to be dilated and filled with blood 

 containing strands of fibrin and a fibrin network in some places. 

 The whole vessel was well-preserved, an elastica interna was 

 present, and the endothelium was intact save in some places 



