XVI I.] 



PRIM A TES. 



317 



The pubis and ischium are short, and widely divergent 

 from each other, so that the thyroid foramen (//{/) is elon- 

 gated in the direction across the main axis of the bones. 

 The symphysis (s) is rather short, and formed by the 

 pubis alone. Each of the apposed surfaces of bone is 



ss 



tif 



ss 



FIG. 114. Ventral surface of right inno- 

 minate bone of Man, 



FIG. 115. Ventral surface of right inno- 

 minate bone of Dog, \. 



si supra-iliac border or crest of the ilium ; ss sacral surface; is iliac surface; ab 

 acetabular border ; pb pubic border ; ib ischial border of ilium ; a acetabulum ; 

 M/"thyroid or obturator foramen ; //tuberosity of ischium ; j symphysis of pubis. 



capped by a plate of fibro-cartilage : these are held to- 

 gether by strong ligamentous fibres, while between them 

 there is usually a more or less perfect synovial cavity. 

 Ankylosis at this spot, so common in the lower Mammalia, 

 very rarely takes place in Man. 



