OS INNOMINATUM. ILIUM. 



89 



Os INNOMINATUM. The os innominatum (os coxae) is an irregular 

 flat bone, consisting in the young subject of three parts, which meet at 

 the acetabulum. Hence it is usually described in the adult as divi- 

 sible into three portions, ilium, ischium, and pubes. The ilium is the 



Fig. 39.* 



superior, broad, and expanded portion which forms the prominence of 

 the hip, and articulates with the sacrum. The iscMum is the inferior 

 and strong part of the bone on which we sit. The os pubis is that 

 portion which forms the front of the pelvis, and gives support to the 

 external organs of generation. 



The ILIUM may be described as divisible into an internal and ex- 

 ternal surface, a crest, and an anterior and posterior border. 



The internal surface is bounded above by the crest, below by a 

 prominent line, the linea ilio-pectinea, and before and behind by 



* The os innominatum of the right side. 1. The ilium ; its external surface. 

 2. The ischium. 3. The os pubis. 4. The crest of the ilium. 5. The supe- 

 rior curved line. 6. The inferior curved line. 7- The surface for the gluteus 

 maximus. 8. The anterior superior spinous process. 9. The anterior inferior 

 spinous process. 10. The posterior superior spinous process. 11. The poste- 

 rior inferior spinous process. 12. The spine of the ischium. 13. The great 

 sacro-ischiatic notch. 14. The lesser sacro-ischiatic notch. 15. The tuber- 

 osity of the ischium, shewing its three facets. 16. The ramus of the ischium. 

 17. The body of the os pubis. 18. The ramus of the pubes. 



