322 FASCIA AND MUSCLES OF THE HORSE 



tour. This part of the muscle is intersected by several tendinous sheets. One of 

 these is particularly distinct, and is attached to the gluteal line on the ilium. This 

 divides the muscle incompletely into superficial and deep strata. The superficial 

 part is inserted by a strong tendon into the summit of the great trochanter, and 

 by a pointed fleshy mass with a tendinous border into the lateral surface of the 

 trochanteric ridge. The deep part is termed the gluteus accessorius ; it is smaller, 

 and arises entirely from the ilium between the gluteal line and the tuber coxse (Fig. 

 580). It has a strong flat tendon which passes over the anterior part or convexity 

 of the trochanter to be inserted into the crest below it. The trochanter is covered 

 here -(vith cartilage, and the trochanteric bursa (Bursa trochanterica) is interposed 

 between the tendon and the cartilage. "■ 



Relations. — Superficially, the skin, lumbo-dorsal and gluteal fasciae, the tensor 

 fasciae latae, gluteus superficialis, and biceps femoris; deeply, the longissimus, the 

 ilium, sacro-iliac and sacro-sciatic ligaments, the gluteus profundus, iliacus and 

 rectus femoris, the iliaco-femoral vessels, the gluteal and internal pudic vessels and 

 nerves, and the great sciatic nerve. 



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



Nerve-supply. — Gluteal nerves. 



4. Gluteus profundus.^ — This much smaller quadrilateral muscle lies under 

 the posterior part of the preceding muscle, and extends over the hip joint, from the 

 superior ischiatic spine to the anterior part of the trochanter major (Fig. 580). 



Origin. — The superior ischiatic spine and the adjacent part of the shaft of the 

 ilium. 



Insertion. — The edge of the anterior part or convexity of the trochanter major 

 of the femur. 



Action. — To abduct the thigh and to rotate it inward. 



Structure. — The muscle is short and thick and contains numerous tendinous 

 intersections. The fibers are directed almost transversely outward over the capsule 

 of the hip joint and converge at the convexity of the trochanter. 



Relations. — Superficially, the gluteus medius and branches of the gluteal vessels 

 and nerves; deeply, the shaft of the ilium, the hip joint, and the rectus femoris 

 and capsularis. 



Blood-supply. — Gluteal artery. 



Nerve-supply. — Anterior gluteal nerve. 



5. Biceps femoris.^ — This large muscle lies behind and in part upon the super- 

 ficial and middle glutei. It extends in a curved direction from the sacral and 

 coccygeal spines to the lateral surface of the stifle and leg (Figs. 267, 292, 580). 



Origin. — (1) The dorsal and lateral sacro-iliac ligaments, the gluteal and 

 coccygeal fasciae, and the intermuscular septum between this muscle and the semi- 

 tendinosus; (2) the tuber ischii. 



Insertion. — (1) A rough eminence on the posterior surface of the femur near 

 the trochanter tertius; (2) the free (anterior) surface of the patella and the lateral 

 patellar ligament; (3) the tibial crest; (4) the crural fascia and the tuber calcis. 



Action. — The action is somewhat complex, because the muscle is composed 

 of three parts, has several points of insertion, and acts on all the joints of the 

 limb except those of the digit. The general action is to extend the limb, as in pro- 

 pelling the body, rearing or kicking, and to abduct it. The anterior part, by its 

 attachment to the posterior surface of the femur and to the patella, would extend 



1 By most anatomists the portion inserted into the crest is termed the gluteus accessorius, 

 but Lesbre considers this to be the deep gluteus, homologous with the gluteus minimus of man. 

 The portion inserted into the trochanteric ridge apparently represents the piriformis of man. 



2 Lesbre considers this to be the scansorius. 



^Apparently the muscle represents the biceps, together with part of the gluteus super- 

 ficialis of man. Hence the names, gluteo-biceps and paramero-biceps have been suggested. 



