OSTEOLOGY AND ARTHROLOGY 



79 



quadrupeds, the iliac bone being, in its entirety, directed 

 much more obhquely downwards and backwards, the relative 

 position of these constituent parts is a little modified : the 

 ilium is in front, the pubis is still internal, but in a more 

 inferior position, and the ischium is behind the cotyloid 

 cavity. We notice this peculiarity of the development of 

 the iliac bone because it is customary to continue to apply to 



6 8 



Fig. 43. — The Left Iliac 

 Bone of the Human 

 Being : External Sur- 

 face, PLACED IN the POSI- 

 TION WHICH it would 

 OCCUPY IN THE SKELETON 



OF A Quadruped. 



I , Cotyloid cavity ; 2, ilium ; 

 3, iliac crest ; 4, anterior iliac 

 crest ; 5, posterior iliac spine ; 

 6, pubis ; 7, tuberosity of the 

 ischium; 8, obturator fora- 

 men ; 9, ischiadic spine. 



Fig. 44. — Left Iliac Bone of a 

 Quadruped (Horse) : External 



Surface. 



I, Cotyloid cavity; 2, ilium, external 

 iliac fossa (directed upward in the horse); 

 3, iliac crest ; 4, anterior iliac spine 

 (directed inwards in the horse, it is the 

 angle of the haunch) ; 5, posterior iliac 

 spine (directed inwards in the horse ; it 

 is the angle of the haunch); 6, pubis; 

 7, tuberosity of the ischium ; 8, obtu- 

 rator foramen ; 9, ischiadic spine, or 

 subcotyloid foramen. 



the osseous regions which correspond to these parts the 

 names by which they were known when independent bones. 



The bones which form the skeleton of the pelvis of quad- 

 rupeds are proportionally more elongated and less massive 

 than those of the human pelvis (Figs. 43 and 44). 



We find, on the external surface of the iliac bone, the 

 cotyloid cavity, whose border is interrupted by the cotyloid 

 notch ; a deep notch which looks downwards. 



