THE PELVIS. 473 



and outer part of the acetabulum. At this point the body 

 contracts and presents a groove bounded above by the coty- 

 loid ridge, along which the tendon of the obturator externus 

 muscle passes. At the posterior part of the neck, just below 

 the sciatic notch, is seen the spinous process which projects 

 inward and backward, and to which is attached the superior 

 gemellus muscle and the lesser sciatic ligament. Below this 

 spine is a smooth pulley-like surface, round which turns the 

 tendon of the obturator internus. As we descend, the next 

 process is rough and large, and called the tuberosity it is 

 covered with cartilage, and presents three faces, one an- 

 terior, which gives origin to the semi-membranosus muscle; 

 and two posterior, from which the semitendinosus and bi- 

 ceps arise. To the outer margin, the adductor magnus, 

 quadratus femoris , and gemellus inferior are attached ; to the 

 inner, the long sacro-sciatic ligament. Between the spine 

 and the tuberosity is the lesser sciatic notch, converted into 

 a foramen by the long sciatic ligament. From the tuber- 

 osity the ramus ascends forward and inward to unite with 

 the pubis, and bounds the inferior and internal portion of 

 the thyroid foramen. It is a flat process, its surfaces pre- 

 senting, externally and internally. Its anterior border 

 bounds, in part, the lower outlet of the pelvis. 



The os-pubis (Fig. 142) is smaller than either the ilium 

 or ischium, and is situated at the front part of the pelvis ; 

 it consists also of a body and processes. The most external 

 portion is regarded as the body; it is thick, and forms the 

 internal and upper part of the acetabulum. Its lower por- 

 tion unites with the body of the ischium ; its upper joins 

 the ilium in the ilio-pectineal eminence. Its inner surface 

 is smooth, and enters into the formation of the anterior 

 pelvic wall. From the body proceeds, transversely inward 

 and forward, a process called the horizontal ramus. The 

 superior surface of this ramus is smooth, and bounded in- 

 ternally by a process or tuberosity, called the spine of the 

 pubis, which gives insertion to Poupart's ligament. From 

 this spine proceed outward two ridges; the posterior is 

 the more elevated and frequently sharp, called the crista } 





