312 Anatomy Applied to Medicine and Surgety. 



spinous process. The third spine corresponds to the lower 

 limit of the spinal membranes, to the exit of the gluteal 

 artery and to the upper border of the sacro-sciatic notch, 

 The lower part of the last piece of the sacrum is opposite 

 the spine of the ischium. 



Landmarks for the Vessels. Gluteal Artery. Ro- 

 tate the slightly flexed thigh inwards, and draw a line 

 from the posterior superior spinous process to the pos- 

 terior part of the upper border of the great trochanter. 

 The junction of the upper and middle thirds of this line 

 will correspond to the point of emergence of the gluteal 

 artery above the pyriformis muscle, and is about opposite 

 to the third sacral spine. 



The sciatic and pudic arteries may be located by iden- 

 tifying the spine of the ischium, in the manner above de- 

 scribed, since they emerge from the pelvis immediately 

 above this spine, Landmarks for the muscles. The glu- 

 teal muscles may be mapped out by remembering their 

 origin and insertion. The pyriformis may be represented 

 by a triangle, with its apex at the anterior part of the up- 

 per border of the great trochanter, and its bas-e corre- 

 sponding to the line drawn between the landmark for the 

 gluteal artery, above, and that for the sciatic and pudic 

 arteries, below. The quadratus femoris, about two inches 

 broad, is situated between the outer surface of the tuber 

 ischii and the posterior surface of the great trochanter, 

 while the obturator internus with the gemelli, above and 

 below it, is situated between these two muscles, i.e., the 

 pyriformis and the quadratus femoris. Landmarks for 

 the nerves. The superficial nerves of the gluteal region 

 are situated as follows : Below the anterior iliac spine are 

 the branches of the external cutaneous ; behind the spine 

 and running towards the great trochanter, the lateral 

 cutaneous of the last dorsal crosses the iliac crest; close 



