140 DK PETER THOMPSON. 



have been partly converted into a tendinous arch. From this 

 Kolhnann argues that it is possible that some of the bundles of 

 the levator ani in man may have been converted into a tendinous 

 arch — the white line ; and he is of opinion that the differences 

 in its development may possibly be due to the influences of 

 pressure and pulling. 



As far as my dissections go, and. these include examples from 

 each group of mammals, I am satisfied that there is no ' white 

 line ' of the pelvic fascia in relation to the pubo- and ilio- 

 coccygei muscles. But in addition to Kolhnann, Lartschneider 

 also refers to the ' white line ' in lower animals. In the stag and 

 horse he figures a white band in the fascia obturatoria, extend- 

 ing from near the origin of the pubo-coccygeus (ischio-anal 

 muscle) ventrally to the back of the symphysis pubis, which he 

 thinks may represent the arcus tendineus of hoofed animals. 



Now in ungulates, neither the pubo-coccygeus nor the ilio- 

 coccygeus are present. There are, however, two muscles arising 

 in close apposition from the internal surface of the ischium, 

 which probably represent the coccygeus and ischio-anal muscles. 

 The obturator intern us is covered with a prominent layer of 

 fascia ; but in none of my dissections did I observe anything 

 resembling the ' white line ' of human anatomy. The obturator 

 fascia, as Lartschneider points out, shows numerous tendinous 

 thickenings, but it is by no means clear that the most marked, 

 or indeed any of these, correspond with the arcus tendineus in 

 man. 



Even in man, in whom the visceral fascia is specially de- 

 veloped, the 'white line' is not always recognisable. When 

 present, as already pointed out, it may or may not coincide with 

 the arcus tendineus of the levator ani. On the other hand, it 

 is more usual to find the tendinous thickening lying upon the 

 inner (upper) surface of the muscle, immediately below its 

 apparent origin from the side wall of the pelvis. 



Apparently the ' white line ' of the pelvic fascia is a special 

 development peculiar to man, though its origin is foreshadowed 

 in lower primates by the fact that the fascia visceralis is fused 

 externally with the upper fascia of the pelvic diaphragm. Its 

 actual appearance seems intimately related to the complete 

 assumption of the erect attitude. Under this condition the 



