CHANGES IN FETAL VESSELS OF THE LIVEK 491 



In several cats one year old they were still wel' -preserved and 

 firmly adherent to the apex of the bladder but in two animals 

 only three months old they could, on the contrary, scarcely be 

 detected and could be traced only a little beyond the base of 

 the bladder. Often, however, when the atropic fibrous sub- 

 stitute is invisible in the contracted state of the bladder it can 

 easily be detected upon distension and it is evident that their 

 presence or absence in the lateral surfaces and the apex of the 

 bladder is probably largely if not wholly dependent upon the 

 fact as to whether or not they gain a secondary attachment to 

 the degenerating urachus. 



Since the sudden marked retraction which occurs in the 

 hypogastric arteries of the lamb can not occur at all in the dog, 

 cat, rabbit and guinea pig in which only a gradual retraction 

 takes place some days or weeks after birth, it would be possible 

 to construct a series beginning with man, in whom retraction is 

 evidently slight, inconstant and always delayed and ending 

 with the sheep and other ruminants in which it is immediate 

 and practically complete a few hours after birth. It has seemed 

 to me that as far as man is concerned the slight amount of the 

 late retraction and the slowness of it, may be due in part at least 

 to the somewhat different relations of the arteries and the bladder 

 to the abdominal wall and peritoneum. In the domestic animals 

 the uninary bladder is practically an intra-peritoneal organ while 

 in man it is extra-peritoneal. Hence in man the hypogastric 

 arteries lie between the peritoneum and the transversalis fascia 

 for a comparatively long distance. Moreover, because of the 

 different position which it occupies in man, evacuation of the 

 distended bladder cannot assist much in the retractions of the 

 vessels in the infant. Moreover, the descent of the bladder 

 from the region of the umbilicus is much more gradual even if 

 finally more pronounced when the adult condition is reached. 

 It is of doubtful value and validity, to be sure, to compare post- 

 natal degenerative processes in animals born in such widely 

 varying states of maturity, which have such varying life cycles 

 and which grow at still more widely varying rates, nevertheless 

 the fact remains that in spite of these differences very similar 



