*ium, which has on its lower edge a tuberosity, the prominent bone on which one sits. Near the upper edge is the spine of the ischium, between which and the posterior 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 extends forward below the obturator foramen, a large opening 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.
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Fig. 64.—Diameters of the pelvis: d, antero-posterior; o b, oblique; t r, transverse. (de Nancrede.)
Anteriorly the ossa innominata support the external organs of generation, while within are the internal organs 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 fossæ. 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
