8o THE ARTISTIC ANATOMY OF ANIMALS 



In trout of this cavity is the ihum. This portion, narrow 

 in the part wliich is next the cavity, is directed forwards and 

 upwards, expanding more and more as it passes upwards. 

 It presents an external or superior surface (external in some 

 animals, superior in others), wliich recalls the external 

 iliac fossa ; and an internal cr inferior surface, at the superior 

 part of which is found the auricular surface for articulation 

 with the sacrum. 



The anterior border of the ilium is rough ; this is the iliac 

 crest, at the extremities of which we find, below or outside, 

 a prominence which corresponds to the anterior superior 

 iliac spine of man ; and internally another projection which 

 corresponds to the posterior iliac spine. 



Immediately above the cotyloid cavity is a rough crest, 

 which is known as the supracotyloid crest, which is, how- 

 ever, no other than the homologue of the sciatic spine. In 

 front of this prominence, the border of the ilium, which is 

 notched, forms the great sciatic notch. 



If, still taking the cotyloid cavity as the point of 

 departure, we proceed inwards — that is, towards the median 

 line of the body — we find the pubis ; if in a posterior 

 direction, the ischium. These two portions, pubis and 

 ischium, limit an oval orifice, the subpubic foramen. 



In the human skeleton, the pubis of one side is united 

 to that of the opposite side, to form the pubic symphysis. 

 In the animals w^hich we are now studying a portion of the 

 ischium enters into the formation of the symphysis ; in 

 other words, it is formed, not only by the body of the pubis, 

 but also by the descending branch or ramus of the pubis 

 and a portion of the ascending branch or ramus of the 

 ischium, which are fused with those of the opposite side. It 

 results that, thougli in the human being the symphysis 

 is short and the ischio-pubic arch large, in quadrupeds it 

 is the opposite. In them the arch is a mere slot, and being 

 formed by the ischium alone, merits the name of the 

 ischial arch. The ischio-pubic symphysis is very large, and 

 forms a horizontal surface relatively extensive, a sort of 

 floor, on which rest certain organs which occupy the 

 cavity of the pelvis. 



