418 MUSCLES AND FASCIAE. 



anterior and posterior surfaces, is situated at the back part and inner side of 

 the thigh. It arises by a thick tendon from the upper and outer part of the 

 tuberosity of the ischium, above and to the outer side of the Biceps and Semi- 

 tendinosus, and is inserted into the inner and back part of the inner tuberosity 

 of the tibia, beneath 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 converge to 

 another aponeurosis, which covers the lower part of its posterior surface, and 

 this contracts into the tendon of insertion. The tendon of the muscle at its 

 insertion divides into three portions; the middle portion is the fasciculus of 

 insertion into the back part of the inner tuberosity ; it sends down an expan- 

 sion to cover the Popliteus muscle. The internal portion is horizontal, passing 

 forwards beneath the internal lateral ligament, to be inserted into a groove 

 along the inner side of the lateral tuberosity. The posterior division passes 

 upwards and backwards, to be inserted into the back part of the outer con- 

 dyle of the femur, forming the chief part of the posterior ligament of the 

 knee-joint. 



The tendons of the two preceding muscles, with those of the Gracilis and 

 Sartorius, form the inner hamstring. 



Relations. By its superficial surface, with the Semitendinosus, Biceps, and 

 fascia lata. By its deep surface, with the popliteal vessels, Adductor Magnus, 

 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 great sciatic nerve. 



Actions. The three hamstring muscles flex the leg upon the thigh. When 

 the knee is semi-fixed, the Biceps, in consequence of its oblique direction 

 downwards and outwards, rotates the leg slightly outwards; and the Semi- 

 membranosus, in consequence of its oblique direction, rotates the leg inwards, 

 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 backwards, as in feats of strength, when the body is thrown backwards 

 in the form of an arch. 



Surgical Anatomy. The tendons of these mnsclos occasionally require subcutaneous division 

 in some forms of spurious anchylosis of the knee-joint, dependent upon permanent 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 narrow sharp-pointed knife between it nmi the skin; the cutting edge 

 being then turned towards the tendon, it should be divided, taking care that the wound in the 

 skin ia not at the same time enlarged. 



MUSCLES AND FASCIAE OF THE LEG. 



Dissection (Fig. 253). The knee should be bent, a block placed beneath it. and the foot kept 

 in an extended 'position ; then make an incision through the integument in the middle lioe of 

 the leg to the ankle, and continue it along the dm-sum of the foot to the toes. Make a second 

 incision transversely across the ankle, and a third in the same direction across the bases of the 

 toes; remove the flaps of integument included between these incisions, in order to examine the 

 deep fascia of the leg. 



The fascia of the ley forms a complete investment to the whole of this region 

 of the limb, excepting to the inner surface of the tibia. It is continuous above 

 with the fascia lata, receiving an expansion from the tendon of the Biceps on 

 the outer side, and from the tendons of the Sartorius, Gracilis, and Semitendi- 

 nosus on the inner side; in front it blends with the periosteum covering the 

 tibia and fibula ; below, it is continuous with the annular ligaments of the ankle. 

 It is thick and dense in the upper and anterior part of the leg, and gives 

 attachment, by its inner surface, to the Tibialis Anticus and Extensor Longus 

 Digitorum muscles ; but thinner behind, where it covers the Gastrocnemius 

 and Soleus muscles. Its inner surface gives off, on the outer side of the leg, 



