1 78 ELEMENTARY ANATOMY. [LESS. 



The innominate bone thus consists of three parts, (i) A 

 widely expanded upper part joins the sacrum and extends 

 down to the socket for the thigh. This is the ilium. 1 



(2) From the thigh-socket a bar of bone runs forwards and 

 inwards. This is the pubis. 2 



(3) Another, stouter, piece of bone curves first downwards 

 from the thigh-socket, and then inwards and then upwards 

 till it meets the pubis. This is the ischium. 3 



FIG. 152. OUTER SIDE OF RIGHT Os INNOMINATUM OF MAN. 

 <7, acetabulum ; at, anterior inferior spinous process of the ilium ; as, anterior 

 superior spinous process of the ilium ; c, crest of the ilium ; ip, ilio-pectineal 

 eminence ; o, obturator foramen ; /, pubis its horizontal ramus ; pi, posterior 

 inferior spinous process ; ps, posterior superior spinous process ; s, spine of the 

 ischium ; t, tuberosity of the ischium. 



The ilium has a wide outer surface (marked by two curved 

 lines), the upper border of which is termed the " crest" and is 

 convex and arched. From the front end of the crest the 

 anterior border descends sharply to the pubis, a blunt promi- 

 nence (called the ilio-pectineal eminence) marking the point 

 of junction. A sharp prominence (termed the anterior supe- 

 rior spinous process] projects from the anterior border of the 

 ilium at its summit, and another the anterior inferior spinous 

 process projects from it a little above the thigh-socket. From 

 the hinder end of the crest of the ilium descends its posterior 

 border, the summit of which is marked by the posterior 

 superior spinous process, separated by a small notch from a 



1 So called from its relation to the ilia, entrails. 



2 la reference to its superficial exoskeleton i.e. the hair. 



3 Named from the Greek TXJ'U, hips. 



