CHANGES IN FETAL VESSELS OF THE LIVER 489 



taneous. This is perhaps never the case if one of them becomes 

 infected, for the infected vessel remains attached longer. 

 But even excluding infections it is not at all likely that the 

 two arteries always rupture simultaneously. 



In a few instances in cats it was also noticed that the retract- 

 ing arteries and urachus drew the vein caudally across the internal 

 surface of the umbilicus. Such occurrences were well described 

 and illustrated in Robin's excellent investigation. 



Robin stated that the obliterated hypogastric arteries usually 

 do not remain attached to the summit of the bladder in rumi- 

 nants and carnivora. As far as sheep are concerned, Robin's 

 statement is confirmed, but in dogs and cats they are almost 

 always attached to the urachus or to a cicatricial formation at 

 the very apex of the bladder. The same statement holds for 

 young rats, guinea-pigs and ral)bits although the minute size 

 of the vessels in these animals makes it much more difficult to 

 observe and trace them with the unaided eye. Besides, it is 

 not rare to find the distal ends of the vessels more or less coiled 

 or tortuous shortly after they become detached from the umbili- 

 cus or even much later in the sheep. Hence it seems strange 

 that a secondary attachment is acquired to the apex of the 

 bladder. This attachment which is a fibrous one is no doul)t 

 due to the fact that before the vessels become detached, the 

 bladder and urachus occupy a position between the con\'erging 

 hypogastric arteries. Hence as the bladder becomes distended 

 they are forced firmly against its sides and may even infold 

 them. After becoming detached the atrophy or retraction of 

 the lateral folds of the peritoneum in which the arteries lie draws 

 them or at least holds them, in intimate contact with the lateral 

 walls and the conical apex of the bladder and the degenerating 

 urachus. Were it not for this fact it would seem to follow that 

 the detached free ends of the hypogastric arteries would be re- 

 tracted passively more and more with each successive dilatation 

 of the bladder until they reached a point far from the apex. 

 After they become attached to the latter further retraction is, 

 of course, impossible and the further obliteration or disapi>ear- 

 ance of these vessels must hence be due to atrophy, degeneration 



