THE INTERNAL MUSCLES OF THE THIGH 281 



dary of the pelvic outlet. It is related posteriorly and externally to the skin and 

 fascia and the semitendinosus ; internally, to the anus and its muscles, the vulva 

 in the female, and the internal pudic artery and nerve (Figs. 452, 453). Below 

 the pelvis the chief relations are: externally, the semitendinosus, biceps, and 

 gastrocnemius, branches of the obturator, femoral, and femoro-popliteal arteries, 

 and the great sciatic nerve and its chief branches; internally, the crus penis 

 and ischio-cavernosus muscle (in the male), and the gracilis; in front, the adduc- 

 tor and the femoral vessels; behind, the skin and fascia. 



Blood-supply. — Obturator and femoral arteries. 



Nerve-supply. — Great sciatic nerve. 



IV. THE INTERNAL MUSCLES OF THE THIGH 

 The muscles of this group are arranged in three layers. 



First Layer 



1. Sartorius (Figs. 186, 202, 203). — This long and rather narrow muscle is the 

 most anterior one of the first layer. It extends from the sublumbar region to the 

 lower and inner part of the stifle. 



Origin. — The iliac fascia and the tendon of the psoas minor. 



Insertion. — The internal straight ligament of the patella and the adjacent part 

 of the tuberosity of the tibia. 



Action. — To flex the hip joint and adduct the limb. 



Structure. — The muscle is very thin at its origin, but becomes thicker and 

 narrower as it passes downward and a little backward. It terminates near the 

 stifle joint on an aponeurosis which blends with that of the gracilis and with the 

 fascia of the leg. 



Relations. — Superficially, the inguinal (Poupart's) ligament, the abdominal 

 muscles, the skin and fascia, and the saphenous vessels and nerve; deeply, the 

 ilio-psoas, quadriceps femoris, and adductor. It forms the anterior boundary of 

 the femoral canal, in which the femoral artery and vein and the deep inguinal 

 lymph glands are situated (Fig. 451). 



Blood-supply. — Femoral artery. 



Nerve-supply. — Femoral and saphenous nerves. 



2. Gracilis (Figs. 186, 199, 202, 203).— This is a wide, flat, quadrilateral 

 muscle, situated behind the sartorius, which it exceeds greatly in extent. 



Origin. — The middle third of the pelvic symphysis, the prepubic tendon and 

 pubo-femoral ligament, and the ventral surface of the pubis behind the prepubic 

 tendon. 



Insertion. — The internal straight ligament of the patella, the internal surface 

 of the tibia in front of the lateral ligament of the stifle joint, and the fascia of 

 the leg. 



Action. — To adduct the limb. It may also rotate it inward. 



Structure. — The muscle arises by a strong tendon, chiefly in common with the 

 opposite muscle. Its direct attachment to the ventral surface of the pelvis is not 

 so extensive as a superficial inspection would suggest. The origin of the muscle 

 presents anteriorly a round perforation for the passage of the external pudic vein. 

 The belly is composed of parallel bundles, and is marked by a superficial furrow 

 which, however, does not indicate a muscular division. It terminates on the inner 

 surface of the stifle on a thin wide tendon which blends in front with that of the 

 sartorius, below with the crural fascia. 



Relations. — Superficially, the skin and fascia, the penis or mammary gland, 

 and the saphenous vessels and nerve; deeply, the pectineus, adductor, semimem- 



