THE MUSCULAR SYSTEM. 161 



of the ischium; insertion, into the digital fossa of the femur; 

 action, rotates the thigh outward ; nerve, the obturator. 



BICEPS. Origin, arises by two heads the long head, from 

 the lower and inner facet of the tuberosity of the ischium by a 

 common tendon to the long head of the semi-tend inosus ; the 

 short head, from the outer lip of the linea aspera, between the 

 vastus externus and the adductor magnus; insertion, outer side 

 of head of fibula, by two portions, on either side of the external 

 lateral ligament of the knee-joint, sending a band forward to the 

 outer tuberosity of the tibia. This tendon forms the outer ham- 

 string; action, flexes the leg upon the thigh; nerve, the great 

 sciatic. 



SEMI-TENDINOSUS. Origin, from a common tendon, to- 

 gether with the long head of the biceps, from the tuberosity of 

 the ischium; insertion, into the inner and upper part of the 

 shaft of the tibia; action, rotates the leg inward; nerve, the 

 great sciatic. 



SEMI-MEMBRANOSUS. Origin, from the outer and upper 

 facet of the tuberosity of the ischium to the outer side and above 

 the origin of the semi-membranosus and the biceps; insertion, 

 into the posterior inner aspect of the inner tuberosity of the 

 tibia, under the internal lateral ligament by three portions the 

 internal portion into the inner side of the internal tuberosity, 

 the posterior portion into the posterior part of the outer condyle 

 of the femur, forming the principal part of the posterior liga- 

 ment of the knee-joint, and middle portion into the posterior 

 aspect of the inner tuberosity; action, flexes the leg upon the 

 thigh; nerve, the great sciatic. 



These two tendons (semi-membranosus and semi-tendino- 

 sus), together with the gracilis and sartorius, form the inner 

 hamstring. 



MUSCLES OF THE LEG. 



Anterior Set. 



TIBIALIS ANTICUS. Origin, from the upper and outer two- 

 thirds of the shaft of the tibia, the interosseous membrane, and 

 the intermuscular septum between it and the extensor longus 

 digitorum; insertion, into the lower and inner aspect of the 

 internal cuneiform bone and base of the first metatarsal bone; 

 action, flexes the foot ; nerve, the anterior tibial. 



EXT KN sou 1' i, MUM; n s 1'm.uris. Origin, from the anterior 

 aspect of the fibula and the interosseous membrane and the 

 intermuscular septum between it and the extensor longus digi- 

 toniin; insertion, into the base of the last phalanx of the great 

 toe; action, extends the great toe; nerve, the anterior tibial. 



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