BONES OF IHE PELVIS. 



15 



Fig. 2. 



part. Below this is a nar- 

 rowed portion called the 

 neck ; from this a pyra- 

 midal process juts out 

 called the spine^ or spi- 

 nous process, affording at- 

 tachment to part of the 

 sacra-sciatic ligament. It 

 varies in length and direc- 

 tion, and is at times of 

 importance obstetrically. 

 In its descent from the 

 neck, the bone bulges out 

 into a protuberance called 

 tuber ischii,{^*) and turn- 

 ing upwards at an acute 

 angle, becomes the as- 

 cending ramus of the 

 ischium. i^'^) The inter- 

 nal surface of this bone 

 is smooth and even, and 



forms one of the inclined planes of the pelvic cavity ; the external 

 is rough, and gives attachment to the sacro-sciatic ligament, and 

 several muscles. The ischium is connected with the ilium and pubes 

 in the acetabulum, and articulated with the sacrum by ligaments. 



Os pubis, is the smallest and most anterior of the three divisions. 

 It has a base or body, two rami, a horizontal and a descending, a 

 spinous process, and a sytnphysis. Its base is the thickest part, and 

 forms the anterior and smaller portion of the acetabulum, beyond 

 which the bone narrows, and proceeding forwards forms the hori- 

 zontal ramus (Fig. 2 *^). This terminates in a wider sheet, and its 

 edge, the point of junction with its fellow bone, is called the sym- 

 physis pubis (Fig. 1 *''). From the inferior part of the symphysis, 

 the descending ramus (Fig. 2 ^^) proceeds downwards to meet the 

 ascending ramus of the ischium, and with it forms one side of the 

 arch of the pubis. On the interior, running along the upper margin 

 of the horizontal ramus, is a ridge, which is part of the linea ilio- 

 pectinea, and at its pubic extremity is a small spinous process, afford- 

 ing an attachment to the pubic end of Pouparfs ligatnent, and near 

 it to the pectineus ; whilst the inner and outer edges of this portion 

 of bone afford insertions to the abdominal muscles. The os pubis is 

 connected with the ilium and ischium in- the acetabulum, with the 

 ascending ramus of the ischium, and with its fellow, by the symphy- 

 sis. In the anterior part of the os innominatum is seen the obturator 

 foramen,{^^) formed by the ischium and pubis, which is nearly filled 

 in the recent state by the obturator ligament ; through the hole at the 

 superior part pass the obturator vessels and nerve. The object 



