432 THE MUSCLES AND FASCIAE. 



4. Posterior Femoral Region. 



Biceps. Semitendinosus. Semimembranosus. 



(Hamstring muscles.) 



Dissection (Fig. 255). Make a vertical incision along the middle of the back of the thigh, 

 from the lower fold of the nates to about three inches below the back of the knee-joint, and 

 there connect it with a transverse incision, carried from the inner to the outer side of the leg. 

 Make a third incision transversely at the junction of the middle with the lower third of the 

 thigh. The integument having been removed from the back of the knee, and the boundaries 

 of the popliteal space examined, the removal of the integument from the remaining part of 

 the thigh should be continued, when the fascia and muscles of this region will be exposed. 



The Biceps (Biceps flexor cruris) is a large muscle, of considerable length, 

 situated on the posterior and outer aspect of the thigh (Fig. 256). It arises by 

 two heads. One, the long head, arises 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 great sacro-sciatic ligament. The 

 femoral, or short head, arises from the outer lip of the linea aspera, between the 

 Adductor magnus and Vastus externus, extending up almost as high as the 

 insertion of the Gluteus maximus ; from the outer prolongation of the linea aspera 

 to within two inches of the outer condyle ; and from the external intermuscular 

 septum. The fibres of the long head form a fusiform belly, which, passing 

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

 covers the posterior surface of the muscle, and receives the fibres of the short 

 head : this aponeurosis becomes gradually contracted into a tendon, which is 

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

 lateral surface of the external tuberosity of the tibia. At its insertion the tendon 

 divides into two portions, which embrace the long external lateral ligament of 

 the knee-joint. From the posterior border of the tendon a thin expansion is 

 given off to the fascia of the leg. The tendon of this muscle forms the outer 

 hamstring. 



Eelations. By its superficial surface, with the Gluteus maximus and the 

 small sciatic nerve, the fascia lata, and integument. By its deep surface, with 

 the Semimembranosus, Adductor magnus, and Vastus externus, the great sciatic 

 nerve, and, near its insertion, with the external head of the Gastrocnemius, 

 Plantaris, the superior external articular artery, and the external popliteal nerve. 



The Semitendinosus, remarkable for the great length of its tendon, is situated 

 at the posterior and inner aspect of the thigh. It arises from the lower and inner 

 impression on the tuberosity of the ischiurn by a tendon common to it and tbe long 

 head of the Biceps; it also arises from an aponeurosis which connects the adjacent 

 surfaces of the two muscles to the extent of about three inches after their origin. 

 It forms a fusiform muscle, which, passing downward and inward, terminates a 

 little below the middle of the thigh in a long round tendon which lies along the 

 inner side of the popliteal space, then curves around the inner tuberosity of the 

 tibia, and is inserted into the upper part of the inner surface of the shaft of that 

 bone nearly as far forward as its anterior border. At its insertion it gives off from 

 its lower border a prolongation to the deep fascia' of the leg. This tendon lies 

 behind the tendon of the Sartorius, and below that of the Gracilis, to which it is 

 united. A tendinous intersection is usually observed about the middle of the muscle. 



Eelations. By its superficial surface, with the Gluteus maximus and fascia 

 lata ; by its deep surface, with the Semimembranosus, Adductor magnus, inner 

 head of the Gastrocnemius, and internal lateral ligament of the knee-joint, the 

 last being separated from the tendon by a bursa. 



The Semimembranosus, so called from its membranous tendon of origin, is sit- 

 uated at the back part and inner side of the thigh. It arises by a thick tendon 

 from the upper and outer impression on the back part of the tuberosity of the 

 ischium, above and to the outer side of the Biceps and Semitendinosus, and is inserted 

 into the groove on the inner and back part of the inner tuberosity of the tibia, be- 



