THE MEDIAL MUSCLES OF THE THIGH 325 



Insertion. — The medial epicondyle of the femur, behind the collateral ligament. 



Action. — To extend the hip joint and to adduct the limb. 



Structure. — The long head, small and pointed above, extends toward the root 

 of the tail, fusing with the sacro-sciatic ligament. Passing downward, it becomes 

 larger and covers in part the posterior aspect of the tuber ischii. A bursa may be 

 found here. Below this it joins the short head, which is larger. The large belly 

 so formed passes downward and forward, covered in great part by the gracilis, and 

 terminates on a short, flat tendon of insertion at the distal end of the femur. 



Relations. — The upper part of the muscle concurs with the sacro-sciatic liga- 

 ment in forming the lateral boundary of the pelvic outlet. It is related posteriorly 

 and laterally to the skin and fascia and the semitendinosus ; medially, to the anus 

 and its muscles, the vulva in the female, and the internal pudic artery and nerve 

 (Figs. 577, 578). Below the pelvis the chief relations are: laterally, the semi- 

 tendinosus, biceps, and gastrocnemius, branches of the obturator, femoral, and 

 posterior femoral arteries, and the great sciatic nerve and its chief branches; 

 medially, the cms penis and ischio-cavernosus muscle (in the male) and the 

 gracilis; in front, the adductor and the femoral vessels; behind, the skin and fascia. 



Blood-supply. — Obturator and femoral arteries. 



Nerve-supply. — Great sciatic nerve. 



m. THE MEDIAL MUSCLES OF THE THIGH 

 The muscles of this group are arranged in three layers. 



First Layer 



1. Sartorius (Figs. 287, 288, 576). — This long and rather narrow muscle is the 

 most anterior one of the first layer. It extends from the posterior part of the sub- 

 lumbar region to the lower and medial part of the stifle, and is directed downward 

 and somewhat backward. 



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



Insertion. — The medial patellar ligament and the tuberosity of the tibia. 



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



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

 and three sided distally. It terminates near the stifle joint on an aponeurosis which 

 blends with that of the gracilis and with the fascia of the leg. 



Relations. — Medially, the inguinal ligament, the abdominal muscles, the skin 

 and fascia; laterally, the ilio-psoas, quadriceps femoris, and femoral nerve. 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. 576). 



Blood-supply. — Femoral artery. 



Nerve-supply. — Saphenous nerve. 



A rare variation is the existence of a small accessory head which arises from the anterior 

 border of the pubis or from the prepubic tendon and joins the normal muscle near the middle of 

 the thigh. 



2. Gracilis (Figs. 276, 287, 575). — This is a wide, quadrilateral muscle, 

 which is situated behind the sartorius, and covers the greater part of the medial 

 surface of the thigh. 



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

 accessory ligament, and the ventral surface of the pubis behind the prepubic ten- 

 don. 



Insertion. — The medial patellar ligament, the medial surface of the tibia in 

 front of the medial femoro-tibial ligament, and the crural fascia. 



Action. — To adduct the limb. 



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



