146 ANATOMY IN A NUTSHELL. 



This muscle, which covers the outer surface of the anterior wall of the pelvis, 

 Ls flat and triangular. 



Origin. (Plate XL1II.) — (1) Margin of inner boundary of obturator 



foramen: (2) inner two-thirds of outer surface of obturator membrane; (3) ten- 

 dinous arch of obturator canal. 



Insertion. (Plate XLVIII.) — Digital fossa of femur. 



ACTION.- Rotates thigh outward and assists in holding head of femur in 

 place. 



\ i.i;\ i. Supply. Second, third, and fourth lumbar through obturator. 



Blood Supply. — Obturator and femoral. 



Weeps. — Description. — (Plate LXY.) — This muscle- — Biceps flexor 

 cruris- is situated on the posterior and outer aspect of the thigh. It is quite 

 large and its tendon forms the outer hamstring. The tendons of the Semi- 

 membranosus, Semitendinosus, Gracilis and Sartorius form the inner hamstring, 

 and lie to the inner side of the knee-joint. 



Origin. — (Plate XLIII.) — By two heads; the long head from the lower 

 and inner impression on the back part of the tuberosity of the ischium, by a 

 tendon common to it and the Semitendinosus, and from the lower part of the 

 greal sacro-sciatic ligament. The femoral, or short head, from the outer lip 

 of the linea aspera, between the Adductor magnus and Vastus externus, ex- 

 tending almost as high as the insertion of the Gluteus maximus; also from the 

 outer prolongation of the linea aspera to within two inches of the outer condyle, 

 and from the external intermuscular septum. 



Insertion. — (Plate LI.) — The fibers of the long head form a fusiform belly, 

 which, pnssing obliquely downward and a little outward, terminates in an 

 aponeurosis which covers the posterior surface of the muscle and receives the 

 fibers of the short head; this aponeurosis becomes gradually contracted into a 

 tendon which is inserted into the outer side of head of fibula, and by a small slip 

 into lateral surface of external tuberosity of tibia. 



A.CTION. Ilexes leg on thigh; rotates semi-flexed knee outward. 



Nerve Supply. — First, second, and third sacral through the great sciatic. 



Blood Supply. Perforating branches of the profunda. 



Semitendinosus. DESCRIPTION. — (Plate LXY.) — This muscle is situated 

 at the posterior and inner aspect of the thigh. It has a remarkably long tendon, 

 which lies behind the Sartorius. and below that of the Gracilis to which it is 

 joined. Its tendon is separated from the internal lateral ligament of the knee- 

 joint by a bursa. About the middle of the muscle there is generally a tendi- 

 nous intersection. 



Origin. (Plate XLIII.) From the lower and inner impression on tuber- 

 osity of ischim by tendon common to it and the long head of Biceps; also from 

 aponeurosis which connect- the adjacent surface of the two muscles to the ex- 

 tent of about three inches a ft ei- their origin. 



[N8ERTION. (Plate LI.) It form- ;i fusiform muscle which, passing down- 

 ward and inward, terminates ;i little below the middle of the thigh in a long, 

 round tendon which li< s along the inner side of the popliteal space, then curves 

 around the inner tuberosity of the tibia and is inserted into the upper part so 



