'2 UR PETER THOMPSON. 



jf the tail, quite close to the median line. It finally terminated 

 in three slender tendons which were inserted into the prominent 

 tuhercles on the under surface of the bodies of the 7th, 8th, 

 and 9th caudal vertebrae. Although the ilio-coccygeus arises 

 in the neighbourhood of the ilio-pectineal line in Echidna, Fclis 

 leo2Mrdus, Fhoca vitulina, Dasyijus sexcinctiis, and many others, 

 and from the side wall of the pelvis at a lower level in 

 Erinaccus curopceus, Lejpus cuniculus, Cavia cohaya, Tliylacinus 

 cynocej)halus, and in Man, the young kangaroo is the first 

 example that I have seen, and as far as I have been able to 

 ascertain, the first that has been recorded, in which the ilio- 

 coccygeus exhibited both attachments in the same animal. Such 

 a disposition illustrates in a marked degree the trans- 

 ference of a part of the ilio-coccygeus from the ilio-pectineal 

 line to a lower level on the pelvic wall. Further, this 

 part has in its turn divided, so that the lower division 

 has continued the descent. In this way the origin of the 

 ilio-coccygeus in the young kangaroo became tripartite, and 

 thus the varying height of the ilio-coccygeus in man and its 

 occasional proximity to the ilio-pectineal line becomes intelligible. 



Passing now to the attachment of the levator ani in the 

 human subject, it arises along an uninterrupted line from 

 the back of the body of the pubis, from the obturator fascia, 

 and from the spine of the ischium. The attachment to the 

 obturator fascia is along a curved line known as the ' white 

 line ' of the levator ani (arcus tendineus musculi levatoris ani, 

 B.N.A.). 



This, it should be pointed out, is not the same structure as 

 the ' white line ' of the pelvic fascia, along which the visceral 

 layer of the pelvic fascia is attached. As regards level, the 

 ' white line ' of the levator ani is extremely variable, that of the 

 pelvic fascia much more constant. Indeed, the line of attach- 

 ment of the levator ani may assume any position between the 

 pelvic brim and a horizontal line drawn through the ischial 

 spine to the back of the body of the pubis. The attachment 

 may in some cases reach within a quarter of an inch of the ilio- 

 pectineal line, and in others it may descend so low as to prac- 

 tically coincide with the level of the ' white line ' of the pelvic 

 fascia. The attachment of the upper and lower fasciae of the 



