OSTEOLOGY 



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pelvic cavity. The latter contains the organs of genera- 

 tion, the rectum, the bladder, the ureters, and the 

 blood-vessels. The pelvic outlet is formed by the pubic 

 arch in front and the coccyx and sacrosciatic ligaments be- 

 hind; the lateral boundaries are formed by the tuberosities 

 of the ischia. The transverse diameter of the pelvic out- 

 let averages 3^ inches in the male and 4% inches in the 

 female. 



FIG. 16. Front view of the pelvis, with its ligaments: i, innominate 

 bone ; 2, crest of ilium ; 3, sacrum ; 4, pubes ; 5, tuberosity of ischium ; 6, 

 anterior superior spine of ilium; a, anterior sacroiliac ligament; b, ilio- 

 femoral ligament; c, obturator membrane; d, symphysis pubis ; , sacro- 

 sciatic ligament (Dorland). 



The sacrum is a curved, triangular bone, situated be- 

 tween the two ossa innominata, and forming, with the 

 coccyx, the posterior part of the pelvis. It is formed of 

 five vertebrae, which, after the twenty-fifth year, become 

 united as one bone. The coccyx consists of four bones 

 articulating with the sacrum, and is subject to fractures 

 and necrosis, conditions that require surgical operations 

 for their cure. Injuries to this bone sometimes occur dur- 



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