228 MYOLOGY, OR ANATOMY OF MUSCULAR SYSTEM 



crest of the tibia, and sends a process to the fascia of the leg. 

 It is below the gracilis tendon, covered by the sartorius, and 

 a bursa separates the three from the internal lateral ligament. 

 It has a thin, oblique intersection in the middle of its belly. 



3. M. Semimembranosus. Origin, tuber ischii above and 

 outside the tendon of the biceps and semitendinosus, and 

 its tendon is grooved posteriorly for the common tendon of 

 those two muscles. Tendon of origin is on the outer side of 

 the muscle for three-fourths the length of the thigh; tendon 

 of insertion, on the opposite side of the muscle, and turns 

 forward and is inserted by four parts (1) into horizontal groove 

 on the back of the inner tuberosity of the tibia; (2) expansion 

 is sent up and in as the posterior oblique ligament of the knee- 

 joint; (3) down to the fascia over the popliteus muscle; (4) 

 to form the short internal lateral ligament of the knee-joint. 



The hamstring muscles descend mostly in contact with 

 each other and are bound down by the fascia lata; inferiorly 

 they diverge the biceps to the outer side, semimembranosus 

 and semitendinosus to the inner side, forming the upper borders 

 of the popliteal space, the inferior margins of which are formed 

 by the heads of the gastrocnemius. 



Varieties. Great reduction in size of the semimembranosus 

 or absence. 



Nerves. Great sciatic, from its internal popliteal division, 

 except that to the short head of the biceps, which is from the 

 external popliteal division. 



Actions. Flex the knee, and then can rotate the tibia and 

 drag it back under the femur; biceps outward, other two 

 inward. Powerful extensors of the hip, and limit flexion of 

 that joint when knee is extended. 



The Internal Femoral Region 



1. M. Pedineus. Origin, iliopectineal line from the ilio- 

 pectineal eminence and spine of the pubis, and slightly from 

 bone in front of this, and from the .fascia over the muscle; 

 insertion, femur behind the small trochanter and upper part 

 of the line passing from this trochanter to the linea aspera. 

 At origin surfaces are frontal, at insertion are sagittal. 



2. M. Adductor Longus (adductor femoris longus). Flat 

 and triangular, internal to the pectineus, on same plane. 



