48() ARTHUR WILLIAM MEYER 



infrequently receives several exceedingly minute venous radicles 

 which lie immediately extra-peritoneally at the ventral surface 

 of the thick fold of fat constantly present in cats between the 

 umbilicus and a point opposite the base of the xiphoid process. 

 These venous radicles become gradually larger proximally and 

 can sometimes be seen to unite and to join the tapering extremity 

 of the unpaired retracted umbilical vein at a point opposite 

 the middle of the xiphoid process. This peculiar relationship 

 was occasionally very evident because all the vessels beginning 

 with the finest veins even, were very full of blood and the umbil- 

 ical vein could be seen without the least difficulty to empty into 

 the left portal. It might at first thought seem probable that 

 this main vein is a para-umbilical or Burow's vein instead of 

 the true umbilical vein, but microscopic as well as gross exami- 

 nation shows this not to be the case. Moreover, it would be 

 remarkable that all trace of the umbilical vein should have dis- 

 appeared in a kitten but ten weeks old, for example. This 

 transformation of the major portions of the umbilical veins into 

 an integral, even if but a temporary, part of the peripheral 

 venous system is particularly significent in its bearing upon the 

 degeneration and disappearance of the vein and the subsequent 

 formation of a round ligament. Occasionally also a large lym- 

 phatic trunk (figs. 4 and 5) several millimeters in caliber runs 

 parallel and adjacent to the vein in the caudal border of the 

 suspensory ligament directly cranial to the vein. The unusual 

 size, distension and beauty of this trunk which joins the larger 

 lymphatic vessels at the hilus of the liver makes it very con- 

 spicuous and it is evident that its presence and that of a con- 

 verted and actively functioning umbilical vein must have a very 

 important bearing on the time of disappearance of the vein and 

 of the suspensory ligament. That the lumen of the umbilical 

 vein may be preserved longer where branches are located was 

 well established by Baumgarten and by Kirchbach ('99) for man. 

 In case of the kitten two weeks old the umbilical vein had 

 completely lost its characteristic walls although the lumen was 

 stil about .75 mm. in size and full of blood. The walls were 

 composed only of an endothelial lining bounded by connective 



