190 THE LOWER EXTREMITIES. 



the pelvis and under Poupart's ligament, gradually di- 

 minishing in size, and terminates in a tendon that is 

 inserted into the lesser trochanter. It serves to flex the 

 thigh on the pelvis and to rotate it outward. The 

 psoas parvus rises from the last dorsal and the first 

 lumbar vertebrae and does not go out of the pelvis. 



The sartorius or tailor muscle is flat and ribbon-like 

 and is the longest muscle in the body. It rises from 

 the anterior superior spine of the ilium and is inserted 

 into the upper inner surface of the shaft of the tibia. 

 B}' it the legs are crossed. It also forms the outer 

 side of an important landmark, Scarpa's triangle, whose 

 base is formed by Poupart's ligament and the inner side 

 by the adductor magnus muscle, which passes from the 

 ramus of the os pubis and the tuberosity of the ischium 

 to the linea aspera. The femoral artery bisects the tri- 

 angle and runs into its apex. 



The bulk of the anterior portion of the thigh is formed 

 by the quadriceps extensor, which is really made up 

 of four muscles, the rectus femoris, whose origin is on 

 the anterior inferior iliac spine and above the acetab- 

 ulum; the vastus externus, which comes from the greater 

 trochanter and the upper linea aspera; and the vastus 

 internus and crureus, which rise from the neck of the 

 femur and the linea aspera. It is inserted into the tu- 

 bercle of the tibia by the ligamentum patella, in which 

 the patella lies. Its action is to extend the leg. 



At the back and forming the buttocks are the three 

 glutei muscles, the glutens maximus, medius, and mini- 

 mus. All these rise from the outer side of the ilium 

 and have their insertion on or about the great troc- 

 hanter. They serve to hold the trunk erect and to 

 extend, abduct, and rotate the thigh. 



Lower down and forming the back of the thigh are 

 the biceps and the semitendinosus and semimembrano- 

 sus muscles. The biceps rises by two heads from the 

 tuberosity of the ischium and the linea aspera and is 

 inserted into the head of the fibula. It is on the outer 



