OSTEOLOGY 157 



inserted a portion of the quadratus lumborum. Upon the 

 ventral border caudad to the articular surface is inserted the 

 abductor caudae intemus, and upon the medial aspect of the 

 pectineal process, ventrad of the acetabulum, is inserted 

 the psoas minor. 



The acetabulum, or cotyloid articular cavity, lies at the 

 junction of the four bones of the innominate. Upon the 

 caudo-ventral border of its rim is situated the cotyloid notch, 

 through which pass the blood vessels and nerves of the hip 

 joint. It may be bridged either by a ligament or by bone. 

 The cranial and ventral borders of the acetabulum are 

 formed by the cotyloid bone, but the caudal border of this 

 is within the cavity and it does not extend to the medial 

 surface of the innominate. It articulates with the three other 

 bones of the innominate, and as previously mentioned, 

 sutures are discernible only in immature animals. 



The ischium comprises the caudo-dorsal portion of the 

 innominate, extending from the acetabulum to (presumably) 

 approximately the center of the sjonphysis. A notable varia- 

 tion is in the caudal border of the ascending ramus, which 

 may incline at such angle that the superior tuberosity may 

 be situated either considerably craniad or considerably caudad 

 of the inferior tuberosity of the ischium. In all other points 

 there is also variation of the ischium, but not to so notable a 

 degree; and there are so many muscles attached to this bone 

 that it is impossible to interpret the differences with any 

 confidence. 



Immediately caudad of the acetabulum upon the dorsal 

 border is the sciatic notch, and adjoining it, the gemellus 

 fossa, from which originates the gemellus inferior. In some 

 specimens it is well marked, but in others its definition is 

 poor. The dorso-caudal angle of the ischium, or superior 

 tuberosity, shows great variation in its precise conformation, 

 but from it originate the semimembranosus anticus when 

 this is present, the second or ischial head of the semiten- 



