THE POSTERIOR FEMORAL REGION. 



433 



neath the internal lateral ligament. The tendon of 

 the muscle at its origin expands into an aponeurosis 

 which covers the upper part of its anterior surface : 

 from this aponeurosis muscular fibres arise, and con- 

 verge to another aponeurosis, which covers the lower 

 part of its posterior surface and contracts into the 

 tendon of insertion. The tendon of the muscle at 

 its insertion gives off certain fibrous expansions ; one 

 of these, of considerable size, passes upward and 

 outward to be inserted into the back part of the 

 outer condyle of the femur, forming part of the pos- 

 terior ligament of the knee-joint ; a second is con- 

 tinued downward to the fascia which covers the 

 Popliteus muscle. The tendon also sends a few 

 fibres to join the internal lateral ligament of the 

 joint. 



The tendons of the two preceding muscles, with 

 that of the Gracilis, form the inner hamstring. 



Relations. By its superficial surface, with the 

 Gluteus rnaximus, Semitendinosus, Biceps, and fas- 

 cia lata ; by its deep surface, with the origin of the 

 Quadratus femoris, popliteal vessels, Adductor mag- 

 nus, and inner head of the Gastrocnemius, from 

 which it is separated by a synovial bursa ; by its 

 inner border, with the Gracilis ; by its outer border, 

 with the great sciatic nerve, and its internal popliteal 

 branch. 



Nerves. The muscles of this region are supplied 

 by the first, second, and third sacral nerves through 

 the great sciatic nerve. 



Actions. The hamstring muscles flex the leg 



O O 



upon the thigh. When the knee is semiflexed, 

 the Biceps, in consequence of its oblique direc- 

 tion downward and outward, rotates the leg slightly 

 outward ; and the Semitendinosus, and to a slight 

 extent the Semimembranosus, rotate the leg inward, 

 assisting the Popliteus. Taking their fixed point 

 from below, these muscles serve to support the pelvis 

 upon the head of the femur and to draw the trunk 

 directly backward, as in raising it from the stooping 

 position or in feats of strength, when the body is 

 thrown backward in the form of an arch. When 

 the leg is extended on the thigh, they limit the 

 amount of ilexion of the trunk on the lower 

 limbs. 



[T'Ml 



Surgical Anatomy. The tendons of these muscles 

 occasionally require subcutaneous division in some forms of 

 spurious ankylosis of the knee-joint dependent upon per- 

 manent contraction and rigidity of the Flexor muscles, or 

 from stiffening of the ligamentous and other tissues sur- 

 rounding the joint, the result of disease. This is effected by 

 putting the tendon upon the stretch, and inserting a nar- 

 row, sharp-pointed knife between it and the skin : the cut- 

 ting edge being then turned toward the tendon, it should be 

 divided, taking great care that the wound in the skin is not 

 at the same time enlarged. The relation of the external 

 popliteal nerve to the tendon of the Biceps must always be 

 borne in mind in dividing this tendon. 

 28 



leg. 



FIG. 258. Muscles of the front of the 



