ISCHIUM. 115 



and coated by cartilage 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 

 f he upper segment of the acetabulum , and before and behind, by the 

 anterior and posterior borders. Crossing this surface in an arched direc- 

 tion, 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 included between the 

 superior curved line and the crest, gives origin to the gluteus medius 

 muscle ; that between the curved lines, to the gluteus minimus 7 and the 

 rough interval between the inferior curved line and the arch of the aceta- 

 bulum, 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 curvecfin its direction like the 

 italic letter y, being bent inwards at its anterior termination, and out\vards 

 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 superior 

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

 anterior inferior spinous process ; the t\vo processes being separated by a 

 notch for the attachment of the sartorius muscle. This border terminates 

 inferiorly in the lip of the acetabuTumT The : posterior 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 internal 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 formation 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 tro- 

 chanteric fossa of the femur. The internal surface is smooth, and some- 

 what encroached upon at its posterior border by the spine. 



The posteiior border of the ischium presents towards its middle a re- 

 markable projection, the spine. Immediately above the spine is a notch 

 of large size, the great sacro-ischiatic, and below the spine the lesser sacro- 

 ischiatic notch ; the former being converted into a foramen by the lesser 

 sacro-ischiatic ligament, gives passage to the pyjrifbrmis muscle, the gluteal 

 vessels and nerve, pudic vessels and nerve, and ischiatic vessels and nerve; 

 and the lesser, completed by the great sacro-ischiatic ligament, to the 

 obturator internus muscle, and to the internal pudic vessels and nerve. 

 The inferior border is thick and broad, and is called the tuberosity. The 

 surface of the tuberosity is divided into three facets ; one anterior, which 

 is rough for the origin of the semi-membranosus ; and two posterior, which 

 are smooth, and separated by a slight ridge for the semi-tendin.osus and 

 biceps muscle. The inner margin of the tuberosity is bounded by a sharp 

 ridge, which gives attachment to a prolongation of the great sacro-ischiatic 



