90 ISCHIUM. 



the anterior and posterior borders ; it is concave and smooth for the 

 anterior two-thirds of its extent, and lodges the iliacus muscle. The 

 posterior third is rough, for articulation with the sacrum, and is 

 divided by a deep groove into two parts ; an anterior or auri- 

 cular portion, which is shaped like the pinna, and coated by carti- 

 lage in the fresh bone ; and a posterior portion, which is very rough 

 and uneven for the attachment of interosseous ligaments. 



The external surface is uneven, partly convex, and partly concave ; 

 it is bounded above by the crest ; below by a prominent arch, which 

 forms the upper segment of the acetabulum ; and before and behind, by 

 the anterior and posterior borders. Crossing this surface in an arched 

 direction, from the anterior extremity of the crest to a notch upon the 

 lower part of the posterior border, is a groove, which lodges the gluteal 

 vessels and nerve, the superior curved line ; and below this, at a short 

 distance, a rough ridge, the inferior curved line. The surface in- 

 cluded between the superior curved line and the crest, gives origin to 

 the gluteus medius muscle ; that between the curved lines, to the glu- 

 teus minimus ; and the rough interval between the inferior curved 

 line and the arch of the acetabulum, to one head of the rectus. The 

 posterior sixth of this surface is rough and raised, and gives origin to 

 part of the gluteus maximus. 



The crest of the ilium is arched and curved in its direction like the 

 italic letter /, being bent inwards at its anterior termination, and out- 

 wards towards the posterior. It is broad for the attachment of three 

 planes of muscles, which are connected with its external and internal 

 borders or lips, and with the intermediate space. 



The anterior border is marked by two projections, the anterior su- 

 perior spinous process, which is the anterior termination of the crest, 

 and the anterior inferior spinous process ; the two processes being se- 

 parated by a notch for the attachment of the sartorius muscle. This 

 border terminates inferiorly in the lip of the acetabulum. The poste- 

 rior border also presents two projections, the posterior superior and 

 the posterior inferior spinous process, separated by a notch. Inferiorly 

 this border is broad and arched, and forms the upper part of the great 

 sacro-ischiatic notch. 



The ISCHIUM is divisible into a thick and solid portion, the body, 

 and into a thin and ascending part, the ramus ; it may be considered 

 also, for convenience of description, as presenting an external and in- 

 ternal surface, and three borders, posterior, inferior, and superior. 



The external surface is rough and uneven, for the attachment of 

 muscles ; and broad and smooth above, where it enters into the forma- 

 tion of the acetabulum. Below the inferior lip of the acetabulum is 

 a notch, which lodges the obturator externus muscle in its passage 

 outwards to the trochanteric fossa of the femur. The internal surface 

 is smooth, and somewhat encroached upon at its posterior border by 

 the spine. 



The posterior border of the ischium presents towards its middle a 

 remarkable projection, the spine. Immediately above the spine is a 



