238 SURGICAL ANATOMY OF 



of the posterior division of the internal iliac, passes out 

 of the pelvis, at the upper part of the great sacro-sciatic 

 notch, and lies between the gluteus minimus and pyri- 

 formis. It may be the seat of aneurism, either idio- 

 pathic or traumatic, and the vessel in either case may be 

 readily reached in actual practice, without attendance to 

 the somewhat complicated directions given for finding 

 it ; in the former case the swelling caused by the posi- 

 tion of the sac, and in the latter the direction of the 

 already existing external wound, would guide the sur- 

 geon. 



The internal pudic artery lies very deep in the gluteal 

 region, and having escaped between the pyriformis and 

 levator ani, emerges from the pelvis at the great sacro- 

 sciatic notch, and winds round the spine of the ischium 

 accompanied by its nerve ; again reaching the pelvis at 

 the lesser sacro-sciatic notch, it lies on the inner surface 

 of the ischium, and is there covered by a process of the 

 obturator fascia (vide Perineum). 



The great sciatie nerve emerges from the greater notch 

 at its lower portion, and lies exactly between the tuber- . 

 osity of the ischium and the great trochanter. 



The intermuscular, cellulo-fatty membranes, which 

 are so extensive in the gluteal region, freely intercom- 

 municate with those within the pelvis, and readily ex- 

 plain the passage of pus either from or into its cavity. 

 Sciatic hernice occasionally exist, a portion of intestine 

 passing down through the greater sacro-sciatic foramen, 

 and having the vessels posterior to its sac. 



The bursa over the great trochanter is sometimes the 

 seat of abscess, which may be mistaken for diseases of 

 the hip-joint. 



The obturator or ischio-pubic region forms the inner 



