The Posterior Limb. 145 



on its lateral, posterior, and medial sides. They are partly covered by 

 the flexors of Group 3, namely, the biceps, sartorius, and gracilis, which 

 must be divided. To begin the dissection, see directions for removing 

 the biceps (p. 148). The position of the sciatic vein (p. 149) should be 

 noted. 



Dissection on the lateral surface posteriorly. 



(a) The glutaeus maximus. Origin in two fleshy portions, joined 

 by an aponeurosis : 



First portion : Fascia covering the sacrum in its entire length. 



This portion is triangular in shape, and is covered posteriorly 



by the first head of the biceps. 

 Second portion : Anteroventral border of the iliac wing, fused 



with the tensor fasciae latae and the first head of the rectus 



femoris; also from the dorsal border through the aponeurosis 



mentioned above. 

 Insertion: Third trochanter. The axis of the first portion 



is transverse, that of the second horizontal. 



Both portions of the muscle should be divided. 



(b) The glutaeus medius. Ventral border of .the wing of the 

 ilium and the iliac crest. Insertion: Greater trochanter. 

 Some of the fibres pass around the medial surface of the tip 

 of the greater trochanter and are inserted in the lateral wall 

 of the trochanteric fossa. 



The muscle should be divided. 



(c) The glutaeus minimus. Origin : Entire lateral surface of the 

 body and wing of the ilium. Insertion : Greater trochanter. 



Remove the entire muscle. The piriformis is in contact with its 

 dorsal margin posteriorly. 



(d) The tensor fasciae latae. Origin: Anterior portion of the 

 ventral border of the wing of the ilium. Insertion: Broad 

 fascia of the lateral surface of the thigh. The muscle is 

 fused with the first head of the rectus femoris in front, and 

 with the second portion of the glutaeus maximus behind. 



(e) The piriformis. Origin: Lateral portions of the second and 

 third sacral vertebrae. Insertion : Tip of the great trochanter. 



The muscle should be divided, care being taken to avoid injury to 

 the nerves and bloodvessels beneath it. 



(f) The gemellus superior. Origin: Tendinous from the ischial 

 spine and fleshy from the body of the ischium immediately 

 in front of it. Insertion: Lateral wall of the trochanteric 

 fossa. 



The muscle extending from the ischial spine to the sacrum is the 

 abductor caudae anterior (p. 183). 



(g) The obturator internus. Origin: Internal extent of the 

 obturator foramen. Insertion: Trochanteric fossa. The 

 muscle passes over the ischium in the lesser sciatic 

 notch, only its insertion portion appearing from the lateral 



