472 THE PELVIS. 



The processes of the ilium are seen upon its circumference. 

 Its superior border is called the crest In the young sub- 

 ject this is an epiphysis, and presents the form of an italic 

 8, looking inward in front, and outward behind. The 

 anterior extremity of the crest presents a projection called 

 the anterior superior spinous process, which gives origin to 

 the sartorius and tensor vaginw femoris muscles, and Pou- 

 part's ligament. 



The posterior extremity of the crest is the posterior supe- 

 rior spinous process, to which the sciatic ligaments are 

 attached. The crest also has an inner margin, from which 

 arises the trans versalis abdominis muscle, an outer margin 

 for the attachment of the external oblique, and an interme- 

 diate space for the internal oblique. The anterior circum- 

 ference of the ilium presents a notch bounded above by the 

 anterior superior spine, and below by the anterior inferior 

 spine. This latter is above the outer part of the acetabulum 

 and gives origin to the rectus femoris muscle. The notch 

 has the gluteus medius attached to it, and an external cu- 

 taneous nerve occupying it. Below and internal to the an- 

 terior inferior spinous process, is a hollow, along which pass 

 fhepsoas magnus and iliacus internus muscles; internal to 

 this hollow and where the ilium unites with the pubis, is 

 a prominence called the ilio-pectineal eminence. The poste- 

 rior circumference, in addition to the posterior superior 

 spinous process, has about an inch and a quarter below the 

 posterior inferior spinous process. Below this spine the 

 ilium becomes notched to form the sciatic notch. 



The ischium (Fig. 142) is the next in size of the bones of 

 the innominatum, and is situated at the lateral and inferior 

 part of the pelvis. It is the bone on which we sit. It con- 

 sists of a body and processes. The body presents a trian- 

 gular or pyramidal form, and has three surfaces, an inter- 

 nal, posterior, and external. The internal surface, called the 

 plane of the ischium, is smooth, broad above and narrow 

 below. The posterior forms a prominent rounded surface, 

 corresponding to the posterior parietes of the acetabulum. 

 The external surface is much excavated and forms the lower 



