ARRANGEMENT OF THE FASCIAE OF THE PELVIS. 141 



pelvic viscera require additional support, and this is prob- 

 ably obtained by a proportionate thickening of the visceral 

 fascia. Obviously there is now a more cogent reason for a 

 firm external attachment, and this seems to be obtained by 

 additional bundles of connective tissue, which strengthen the 

 fasciffi and lead to the formation of the ' white line ' 



Since, then, in mammals below primates there is no visceral 

 pelvic fascia similar to that occurring in man and the orang- 

 utan, one may, in conclusion, ask, What is the origin of the 

 fascia ? It is difficult to give a definite answer to this ques- 

 tion. But at any rate we know that a fibrous sheath 

 envelops the obliterated hypogastric artery, and the vessels 

 supplying the bladder, uterus, vagina, and rectum, and it may 

 be that the supporting layers of the pelvic fascia are primarily 

 derived from this, by lateral extension on to the fascia covering 

 the upper surface of the levator ani. There is one circumstance 

 that seems to lend some support to this view, namely, that in 

 the orang-utan the visceral layer of the pelvic fascia, at least 

 in its hinder part, is double, and some of the vessels derived 

 from the hypogastric trunk are situated between the two layers. 

 But further observations are necessary to elucidate this point. 



