GLUTEUS MAXIMUS 351 



Structure. — The ori<>;in is 1)v fleshy and tendinous fil)res intermingled. The 

 filjres then run i);irallel to one another to a tendinous insertion Ijetween the iliaeus 

 and the adductor brevis. The direeti(jn of the surfaces changes so that that which 

 looks forwards ahove is directed outwards below. 



Nerve-supply. — From the lumbar plexus (through the third and fourth 

 lumbar nerves), by a branch of the anterior crural nerve, which, after passing 

 behind the femoral artery and vein, enters the muscle aljout the middle of its 

 external border. \Mien there is an accessory obturator nerve, it passes over the 

 brim of tlie pelvis to supply this muscle at the upper part of its anterior surface. 

 Occasionally the muscle receives a branch upon its deep surface from the anterior 

 division of the obturator nerve. 



Action. — To flex and at the same time adduct the thigh; as, for example, in 

 crossing the legs, when one thigh is brought forwards and inwards to place it in 

 front of the other thigh. It is also a slight external rotator. Its predominant 

 action is that of flexion, as is indicated by the fact that it receives the same nerve- 

 supply as the sartorius and ilio-psoas. The tendency which it has to adduct during 

 flexion is counteracted by the slight abduction produced by the sartorius. They 

 will together produce the slight external rotation, which is observed during the 

 advance of the leg in walking. 



Relations. — In front, the puVjic portion of the fascia lata, the femoral and 

 profunda vessels, and at its insertion the psoas and iliaeus muscles; behind, the 

 adductor brevis, obturator externus, hip-joint, and obturator nerve. 



Variations. — Sometimes a slight blendiug of the lower fibres of the pectiueus with the 

 adductor lousus has been observed. 



THE GLUTEAL MUSCLES 



These are arranged in three layers. 



First Layer 



The first layer consists of two muscles — the gluteus maximus and the tensor 

 vaginae femoris. 



1. GLUTEUS MAXI^IUS 



Tlie gluteus maximus (figs. 291 and 303) — named from its great size and from 

 the region which it occupies {ykouTo^ = the buttock) — is a very thick and strong 

 rhomboidal sheet. 



Origin. — (1) The posterior fifth of the outer lip of the crest of the ilium, and 

 the outer surface of the ilium between the outer lip of the crest and the superior 

 gluteal line; (2) the lumbar aponeurosis betAveen the posterior superior spine of the 

 ilium and the side of the sacrum; (3) the lateral portion of the posterior surface of 

 the two last pieces of the sacrum; (4) the side of the coccyx; (5) the back of the 

 great sacro-sciatic ligament; (6) in front of its attachment to the ilium a few of its 

 fibres arise from the strong process of the fascia lata which invests the gluteus 

 mcdius. 



Insertion. — (1) The upper part of the strong aponeurosis of the fascia lata, 

 called the ilio-tibial band; (2) the gluteal ridge of the fenuir which leads from tlie 

 lower l)order of the greater trochanter to the linea aspera; (3) the adjacent part of 

 the tendinous origin of the vastus externus. 



Structure. — Its origin is almost entirely fleshy, a few tendinous fibres only 

 being intermingled between the coarse bundles which rim parallel to one anotlier 

 downwards and outwards to the aponeurosis of insertion. The U])per half of this 

 aponeurosis passes over the outer surface of the great trochanter to be attached to 

 the u})per part of the ilio-til)ial band. Lower down the insertion consists of short 



