176 



THE SKELETON 



The inferior aperture, or outlet, of the minor pelvis is very irregular, and en- 

 croached upon by three bony processes: the posterior process is the coccyx, and 

 the two lateral processes are the ischial tuberosities. They separate three notches. 

 The anterior notch is the pubic arch, and is bounded on each side by the conjoined 

 rami of the pubes and ischium. Each of the two remaining gaps, bounded by the 



Fig. 211. — The Male Pelvis. 



ischium anteriorly, the sacrum and coccyx posteriorly, and the ilium above, cor- 

 responds to the greater and lesser sciatic notches. These are converted into 

 foramina b}^ the sacro-tuberous (great sacro-sciatic) and sacro-spinous (small 

 sacro-sciatic) ligaments. 



The position of the pelvis. — In the erect position of the skeleton the plane of the pelvic 

 inlet forms an angle with the horizontal plane, which varies in individuals from 50° to 60°. 



Fig. 212. — The Female Pelvis. 



The base of the sacrum in an avera^^c pelvis lies nearly ten centimetres (four inches) above the 

 upper inar^ciii of the symijhy.sis jjubis. 



The axis of the pelvis. — This is an imaginary curved line drawn through the minor pelvis 

 at right angles to the planes of the inlet, cavity, and outlet through their central points. 



As the posterior wall, formed by sacrum and coccyx, is nearly five inches long and concave, 

 and the anterior wall at the symphysis pubis one one and a half to two inches long, it follows 

 that the a.xis must be curved. 



