INNOMINATE BONE. 



95 



and less strongly marked, extends from the space between the anterior 

 spinous processes to the middle of the great sciatic notch. The space be- 

 tween the crest and the superior curved line has the form of a curved triangle, 

 broad behind and pointed in front, and gives attachment to the gluteus 

 medius muscle, while that between the two curved lines gives attachment 

 to the gluteus minimus. The internal surface of the ilium is divided into 

 three parts. The anterior of these, the largest, is called the iliac fossa; it 

 is concave and smooth, and towards the middle of it the bone is very thin. 

 The posterior part is subdivided ; presenting inferiorly for cartilaginous 

 articulation with the sacrum the smooth but uneven auricular surface, broad 

 in front and extending to the posterior inferior spine behind ; and superiorly 

 a more uneven and rough surface for the attachment of ligaments. The 

 third part, entering into the formation of the true pelvis, is not dis- 

 tinguished by any mark in the adult from the ischium and os pubis ; 

 it is separated from the iliac fossa by a smooth border, the iliac portion of 

 the ilio-pectineal line, which extends from the auricular surface to the pubic 

 spine. 



Fig. 86. EIGHT Os INNOMINATUJI, 



FROM THE INNER OR PELVIC 

 SURFACE. i 



2, 3, 4, 5, 13, 16, 17, and 18, 

 indicate the same parts as in the 

 preceding figure ; 19, iliac fossa ; 

 20, ilio-pectineal line or brim of 

 the true pelvis, ending at 24 ; 21, 

 auricular cartilaginous sacro-iliac 

 surface ; 22, rough tuberculated 

 surface for the posterior sacro-iliac 

 ligaments ; 23, oval surface of the 

 symphysis pubis ; 24, spinous pro- 

 cess of the os pubis, terminating the 

 crest of the pubis and the ilio- 

 pectineal line ; between 17 and 

 20, the pelvic surface of the ilium. 



The os pubis or os pectinis 

 forms the anterior wall of the 

 pelvis, and bounds the obtu- 

 rator foramen in the upper 

 half of its extent. At its 

 outer and upper extremity it 

 forms a part of the aceta- 

 bulum ; at its inner extremity 

 it presents an elongated oval surface, articulating by fibro-cartilage 

 with the bone of the opposite side, its junction with which is called the 

 symphysis pubis. The part which passes downwards and outwards below 

 the symphysis is called the inferior or descending ramus, the upper part is 

 called the superior (or horizontal) ramus, and the flat portion between the 

 rami may be distinguished as the body. The deep or pelvic surface of the 

 os pubis is smooth ; the outer surface is roughened near the symphysis by 

 the attachments of muscles. At the superior extremity of the symphysis 

 is the angle of the pubis, and extending outwards, from this on the superior 

 border is the rough crest, terminating in the projecting spine. The descend- 

 ing ramus is flat from before backwards ; the superior or ascending ramus 

 becomes prismatic, and increases in thickness as it passes upwards and out- 



13 



