OSTEOLOGY. 33 



junction of the three bones, with a narrow rim above, and incom- 

 plete below, where it communicates with the sub-pubic notch. 

 It receives the femoral head. 



The obturator (or oval) foramen is composed of the pubis and 

 ischium, and forms part of the lower pelvic boundary, when 

 closed in by the external and internal obturator muscles. 



THE PELVIS. 



This cavity has an inlet bounded above by the sacrum, below by 

 the pubes, laterally by the ilia. 



It has four diameters, a vertical, from the sacrum to the anter- 

 ior pubic symphysis, of %\ inches, a horizontal, between the 

 pectineal eminences, of Z^^ inches, and two oblique, from the 

 sacro-iliac joints to the pectineal eminences, of Sy^^- inches. 



It also has an outlet through which pass the rectum and genital 

 organs, bounded above by the summit of the sacj'um, below by the 

 upper surface of the ischia, laterally by the sacro-ischiatic liga- 

 ments. 



Ithas two diameters, a vertical, of 61"^ inches, from the sacrum 

 to the ischium, and a transverse, of yy-Q inches, between the supra- 

 cotyloid crests. 



The pelvis of the mare is much more roomy than that of the 

 male, being more marked in its transverse diameters. 



THE THIGH. 



This consists of one bone, the femur. 



THE FEMUR. 



The femur lies between the pelvis above and the tibia below, 

 having a general direction downward and forward. 



It has a shaft and upper and loiver extremities. 



The shaft has — 



An external, anterior and internal face, all smooth and convex, 

 and d. posterior, rough and irregular. 



The posterior face shows in its upper one-third internally a 

 rough elevation, the lesser or internal trochanter, a rough surface 

 for the att'ichment of the pectineus and adductor magnus, below 

 a deep groove and a number of rough elevations, the supra-co7idy- 

 loid crest ; in its upper third rough lines and crests. 



