426 A MANUAL OF ANATOMY 



fascia, and so the depression in that region is filled up. The deef 

 fascia forms a part of the fascia lata. Over the fleshy part o: 

 the gluteus maximus it is thin, but, at the insertion of the muscle 

 and over the anterior two-thirds of the gluteus medius, it is dense 

 In these latter situations it gives insertion to a considerable par' 

 of the gluteus maximus, and origin to the superficial fibres of th( 

 gluteus medius in its anterior two-thirds. In passing from th( 

 gluteus medius on to the gluteus maximus it straps down the uppei 

 border of the latter muscle. 



Muscles. Gluteus Maximus — Origin. — (i) The posterior 2 inches 

 of the outer lip of the iliac crest ; (2) the upper part of the rougl 

 surface on the dorsum ilii between this part of the crest and th( 

 superior gluteal line ; (3) the posterior lamina of the lumbal 

 aponeurosis ; (4) the lateral part of the back of the fourth anc 

 fifth sacral vertebrae ; (5) the back of the upper three coccygea 

 vertebrae close to the lateral border ; and (6) the superficial surface 

 of the great sacro-sciatic ligament. 



Insertion. — (i) Rather more than the upper half of the muscle is 

 inserted between two laminae of the fascia lata on the upper anc 

 outer part of the thigh ; (2) the superficial fibres of rather less thar 

 the lower half are also inserted into the fascia lata, but the deej 

 fibres of this portion are inserted into the gluteal ridge of the femur 

 The part of the fascia lata which gives insertion to the gluteus 

 maximus is known as the ilio- tibial band. 



Nerve-supply. — ^The inferior gluteal nerve from the sacral plexus 

 which enters the muscle on its deep or anterior surface in its lowei 

 third. 



The direction of the coarse fasciculi of the muscle is downwards 

 and outwards. 



Action. — Acting from its origin the muscle extends the thigh upor 

 the pelvis, as in rising from the sitting posture, or ascending a stair. 

 The upper part, acting alone, would abduct the thigh, and the lower 

 part would adduct it and rotate it outwards. The muscle also takes 

 part in the completion of extension of the knee-joint, and in the 

 maintenance of extension, as in standing, through means of the 

 ilio-tibial band of the fascia lata. Acting from its insertion the 

 muscle extends the pelvis upon the thigh, as in raising the trunk 

 from the stooping posture. 



The gluteus maximus, which is quadrilateral, has a short uppeij 

 border which is bound down to the gluteus medius by the fascic 

 lata, and a long lower border which is free. | 



Deep Relations. — ^These, from above downwards, are as follows 

 the posterior fleshy third of gluteus medius ; superficial divisioi 

 of gluteal artery ; extrapelvic part of pyriformis ; great and smal 

 sciatic nerves ; inferior gluteal nerve ; sciatic and internal pudi< 

 arteries ; pudic nerve ; nerve to obturator internus, supplying 

 branch to gemellus superior ; common nerve to gemellus inferior am 

 quadratus femoris ; gemellus superior ; extrai)elvic part of obturate 

 internus ; gemellus inferior ; quadratus femoris ; crucial anastomosi 



