THE PELVIS AND THE GENITAL ORGANS. 163 



ium, which has on its lower edge a tuberosity, the promi- 

 nent bone on which one sits. Near the upper edge 

 is the spine of the ischium, between which and the pos- 

 terior inferior spine of the ilium is the greater sacro-sciatic 

 notch for the passage of vessels and nerves, including 

 the sciatic nerves. From the tuberosity the ramus ex- 

 tends forward below the obturator foramen, a large open- 

 ing between the ischium and the pubes, also for the 

 passage of vessels and nerves, to meet the pubes, the 

 last and smallest of the three bones which go to make 

 up the os innominatum. 



The anterior surface of each pubes presents a crest, 

 ending externally in a spine, and the two pubic bones 

 join in front in the symphysis pubis. The bone gets 

 its name from the growth of pubic hairs over this region 

 at puberty. 



FIG. 64. Diameters of the pelvis: d, antero-pos tenor; ob, oblique; 

 t r, transverse, (de Nancrede.) ' 



Anteriorly the ossa innominata support the external 

 organs of generation, while within are the internal or- 

 gans of generation. On the inner surface of the ilium, 

 slightly above the level of the acetabulum, is the ileo- 

 pectineal line, above which lie the iliac fossce. A plane 

 drawn through the prominence of the sacrum, the ileo- 

 pectineal lines, and the upper margin of the symphysis 

 pubis serves to divide the upper or false pelvis from 

 the lower or true pelvis. The false pelvis, which is 

 the larger, serves to support the intestines and to 



