3i8 THE PELVIC GIRDLE. [CHAI-. 



The posterior and inferior border of the ischium is thick- 

 ened and rounded, and distinguished as the tuber ischii (//). 

 Above this, on the hinder border of the same bone, is a 

 smooth, hollowed surface, called the lesser sciatic notch, 

 surmounted by an angular prominence called the spine ; 

 above the spine the edge of the ischium passes into the 

 great concavity of the posterior or ischial border of the 

 ilium, and which is called the great sciatic, or, more pro- 

 perly, ilio-ischiatic notch. The strong ligaments (sacro- 

 sciatic) which pass from the side of the pseudo-sacral and 

 caudal vertebrae, the one to the tuber and the other to the 

 spine of the ischium, convert these notches in the living 

 body into foramina. 



The anterior or superior (in the vertical position) outlet of 

 the pelvis is subcircular, usually rather broader from side to 

 side than from the vertebral to the pubic border. Its plane 

 is not far from a right angle with the axis of the vertebral 

 column. The posterior outlet is also very wide. In con- 

 sequence of the great curve of the sacrum, and the short- 

 ness of the symphysis, the axis of the whole pelvis is 

 strongly curved. 



In all the Simiina the innominate bone, especially the 

 iliac portion, is more elongated than in Man ; the anterior 

 outlet of the pelvis is longer from above downwards, nar- 

 rower, and more oblique; the tuberosities of the schia 

 are more everted, and the spine and sciatic notches less 

 marked. 



In the highest forms, such as the Gorilla and Chimpanzee, 

 the upper part of the ilium is expanded, flattened, and 

 everted, the iliac surface being even wider than in Man, 

 though much flatter ; but in the Baboons and Monkeys, 

 the whole ilium is long and narrow, the sacral surface rises 

 considerably above the sacral articulation, the iliac surface 



