130 PRACTICAL ANATOMY. 



inferior portion of the ischium is called the tuberosity (in 

 German, the " Sitz-beine," as the tuberosities support the 

 weight of the body in the sitting posture). It presents 

 an outer and inner border and an intermediate surface of 

 bone. To the outer lip is attached the quadratus femoris 

 and adductor magnus muscles. The inner lip presents a 

 sharp crest, for the attachment of the great sacro-sciatic 

 ligament; above this is the groove for the internal pudic 

 vessels and nerve ; it affords attachment also to the trans- 

 versus perinei and erector penis muscles. The inter- 

 mediate surface is rough, for the attachment of muscles. 

 The ascending ramus of the ischium is slender and flat- 

 tened, and joins the descending ramus of the pubes, com- 

 pleting the obturator foramen. Its external surface is 

 rough, for muscular attachment; internally it is smooth 

 and forms part of the anterior wall of the pelvis ; at its 

 inferior part is the continuation of the groove for the 

 pudic vessels and nerve. Its inner border is everted, and 

 affords attachment to the crus penis. The outer border 

 is sharp, and forms part of the circumference of the 

 obturator foramen, and affords attachment to the obtu- 

 rator membrane. 



On the outer surface of the os innominatum, near its 

 centre, is a large, cup-like cavity for articulation with the 

 head of the femur. It is called the acetabulum, or coty- 

 loid cavity. It presents a rim and inner surface. The 

 rim is prominent, elevated above the surface of the bone, 

 strong and heavy above, but deficient at its inferior por- 

 tion, where it presents a notch the cotyloid for the 

 passage of vessels and nerves into the hip-joint. The 

 inner surface presents a ribband of articular cartilage, 

 which skirts the inner margin of the cavity. It is about 

 one inch broad and deficient below. The central por- 

 tion is rough, for the attachment of the round ligament 



