THE LATERAL MUSCLES OF THE HIP AND THIGH 321 



Action. — To tense the fascia lata, flex the hip joint, and extend the stifle joint. 



Structure. — The muscle arises by a rather small head, about two inches (ca. 

 5 cm.) wide, on the antero-inferior eminence of the tuber coxae. Below this the 

 belly spreads out and terminates in the aponeurosis about midway between the 

 point of the hip and the stifle. Many fibers arise from an intermuscular septum 

 between this muscle and the superficial gluteus; this septum is attached to the lat- 

 eral border of the ilium. The aponeurosis fuses with the fascia lata, which may be 

 regarded practically as the tendon of insertion; it detaches a lamina which passes 

 with the tendon of insertion of the superficial gluteus to the lateral border of the 

 femur. 



Relations. — Laterally, the skin and fascia; medially, the obliquus abdominis 

 externus, the iliacus, superficial gluteus, rectus femoris, and vastus lateralis, branches 

 of the circumflex iliac, ilio-lumbar, and iliaco-femoral arteries, and the anterior 

 gluteal nerve; anteriorly, the prefemoral Ijonph-glands. A considerable quantity 

 of connective tissue is found between the deep face of the muscle and the abdominal 

 wall. 



Blood-supply. — Circumflex iliac, ilio-lumbar, and iliaco-femoral arteries. 



Nerve-supply. — Anterior gluteal nerve. 



2. Gluteus superficialis (Fig. 267). — This muscle lies behind and partly 

 underneath the tensor fasciae latae. It is triangular and consists of an anterior and 

 a posterior head united by the gluteal fascia. 



Origin. — (1) The tuber coxae and the adjacent part of the lateral border of 

 the ilium; (2) the gluteal fascia. 



Insertion. — The third trochanter of the femur. 



Action. — To abduct the limb, flex the hip joint, and tense the gluteal fascia. 



Structure. — The anterior head of the muscle is not completely separable (ex- 

 cept artificially) from the tensor fasciae latae, since both muscles are attached to an 

 intermuscular septum. The attachment to the border of the ilium is by means of 

 an intermuscular septum, which passes beneath the thick lateral border of the 

 gluteus medius and furnishes origin to fibers of both muscles. The posterior head 

 arises from the deep face of the gluteal fascia, and so indirectly from the dorsal 

 sacro-iliac ligament. The two heads unite and terminate on a strong flat tendon, 

 which is inserted into the edge of the third trochanter of the femur, under cover of 

 the biceps femoris. 



Relations. — Superficially, the skin, fascia, and 'biceps femoris; deeply, the 

 gluteus medius, iliacus, rectus femoris, and branches of the iliaco-femoral vessels; 

 in front, the tensor fasciae latae; behind, the biceps femoris. 



Blood-supply. — Gluteal and iliaco-femoral arteries. 



Nerve-supply. — Anterior gluteal nerve. 



3. Gluteus medius (Figs. 268, 580). — This is a very large muscle which covers 

 the gluteal surface of the ilium and the greater part of the lateral wall of the pelvis, 

 and extends forward also on the lumbar part of the longissimus dorsi. 



Origin. — (1) The aponeurosis of the longissimus dorsi, as far forward as the 

 first lumbar vertebra; (2) the gluteal surface and tubera of the ilium; (3) the dorsal 

 and lateral sacro-iliac and sacro-sciatic ligaments, and the gluteal fascia. 



Insertion. — (1) The svunmit of the trochanter major of the femur; (2) the crest 

 below the trochanter; (3) the lateral aspect of the trochanteric ridge. 



Action. — To extend the hip joint and abduct the limb. By its connection 

 with the longissimus a muscular mass is formed which is one of the chief factors in 

 rearing, kicking, and propulsion. 



Structure. — The anterior extremity of the muscle is narrow and thin, and lies 



in a depression on the surface of the longissimus, from the strong aponeurosis of 



which the fibers take origin. The pelvic portion of the muscle is very voluminous, 



and forms the bulk of the muscular mass which gives the haunch its rounded con- 



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