THE GLUTEAL REGION 415 



insertion of the greater part of the glutseus maximus, they re- 

 unite to form the strong ilio-tibial tract (p. 401). 



The Glutaeus Maximus passes distally and laterally from 

 the posterior part of the iliac crest and the dorsum of the sacrum 

 to its insertion into the deep fascia and the gluteal tuberosity 

 of the femur. It is supplied by the inferior gluteal nerve (L. 5, 

 S. i and 2) and acts as an extensor, abductor, and lateral rotator 

 of the thigh. Owing to the great bulk of the muscle,, it is ex- 

 tremely difficult to determine fluctuation under cover of it. 

 The fasciculi of which it is made up are very coarse and can 

 readily be separated without damage. They run distally and 

 laterally, and incisions into the buttock are therefore made in 

 the same direction. In flexion of the thigh the posterior border 

 of the greater trochanter passes backwards beneath the upper 

 border of the glutseus maximus when the muscle is well developed. 

 The movement of medial rotation at once disengages the tro- 

 chanter, and the muscle slips off with an audible sound. The 

 condition, which is termed " snapping-hip," may be produced 

 voluntarily, and it was formerly thought to be due to a partial 

 subluxation at the joint. A layer of fat underlies the glutseus 

 maximus, and it may be the site of cellulitic infection following 

 intra-pelvic or ischio-rectal abscesses. The infection spreads 

 through the greater or lesser sciatic foramen, and it penetrates 

 the parietal pelvic fascia, which closes the foramina, by tracking 

 along the gluteal and the internal pudendal vessels (p. 417). 

 A large and constant bursa intervenes between the muscle and 

 the ischial tuberosity, and when inflamed gives rise to a painful 

 swelling. Such a bursitis requires to be differentiated from a 

 gumma and from a cold abscess (p. 522), which may both occur 

 in this situation. 



Two other bursce are found near the insertion of the muscle, 

 one between its fascial insertion and the greater trochanter (p. 

 433) and the other between its tendon and the vastus lateralis. 

 They are both liable to tuberculous synovitis, and the resulting 

 cold abscess may spread (i) distally along the lateral surface of 

 the thigh under the fascia lata or (2) backwards and distally 

 under the glutseus maximus to point in the gluteal fold. 



These bursae are frequently infected with tuberculous disease 

 and may be approached, by a U-shaped incision. The anterior 

 limb of the incision lies behind the posterior border of the 

 tensor fasciae latae, and the posterior limb divides the proximal 

 part of the insertion of the glutseus maximus. The transverse 



