OSSA INNOMINATA. 97 



SECT. IV. - OF THE OSSA INNOMINATA. 



(Os Cozauz, ou des Isles.) These bones, two in number, are 

 situated one at either side of the sacrum, and constitute the la- 

 teral and anterior parietes of the pelvis; forming, along with the 

 sacrum and coccyx, the whole of this latter cavity. 



The os innominatum, from having been, in its original state, 

 in three pieces, notwithstanding they subsequently coalesce firm- 

 ly in the adult, and preserve scarcely any vestige of their pri- 

 mitive distinction, is divided by anatomists into ilium, ischium, 

 and pubes. 



Os lliumj (Ilion.) This, the largest of the three portions, 

 forms all the upper rounded part of the os innominatum, and is 

 the haunch bone of common language. Its superior margin is 

 a semicircle, rather thicker towards the extremities than in the 

 middle. The inequality, when viewed from above, is very ap- 

 parent, as well as a slight curvature resembling the letter S. 

 This margin of the bone is called its crest or spine, presents an 

 internal lip for the origin of the transversalis abdominis muscle, 

 an external one for the insertion of the obliquus externus, and 

 an intermediate edge for the origin of the obliquus internus. 

 The anterior extremity of the spine is terminated by a project- 

 ing point, called the anterior superior spinous process, from 

 which arise the tensor vaginas femoris, the sartorius, and the 

 beginning of Poupart's ligament. The posterior extremity of 

 the crest is also projecting and pointed, but less so than the 

 other, and obtains the appellation of the posterior superior spi- 

 nous process. 



The anterior margin of the os ilium is unequal, and divided 

 into two portions, of nearly the same length, by a strong, well- 

 marked projection, the anterior inferior spinous process, which 

 is placed an inch and a half below the anterior superior, and 

 gives origin to the rectus femoris. This margin joins with the 

 pubes by a large flattened elevation, called the ilio pectineal pro- 

 tuberance. Between the latter and the anterior inferior spinous 

 process, a concavity exists which is occupied by the junction of 

 the psoas magnus and iliacus internus muscles, where they pass 

 under Poupart's ligament. Between the two anterior spinous 



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