608 DISSECTION OF THE LEG. 



Above, it is continuous with the investing membrane of the thigh, and 

 receives offsets from the tendons about the knee ; and below, it joins the 

 two annular ligaments. Externally it is continued uninterruptedly from 

 the one aspect of the limb to the other, but internally it is fixed to the 

 edge of the tibia. Veins are transmitted through it from the deep to the 

 superficial vessels. 



Dissection. The fascia is to be divided along the centre of the leg as 

 far as the heel, and is to be taken from the surface of the gastrocnemius 

 muscle. By fixing with a stitch the inner cut head of the gastrocnemius, 

 the fibres of the muscle will be more easily cleaned. 



SUPERFICIAL LAYER OP MUSCLES. In the calf of the leg there are 

 three muscles, gastrocnemius, soleus, and plantaris, which extend the 

 ankle. The two first are large, giving rise to the prominence on the sur- 

 face, and end below by a common tendon ; but the last, inconsiderable in 

 size, is chiefly tendinous. 



The GASTROCNEMIUS (fig. 207, A ), the most superficial muscle, is ten- 

 dinous along the middle, and has above two distinct pieces or heads, which 

 connect it with the condyles of the femur. The inner head of origin is 

 attached by a large tendon to an impression at the posterior aspect of the 

 inner condyle, behind the insertion of the adductor magnus, and by fleshy 

 fibres to the line above the condyle. The outer head is fixed by tendon 

 to a pit on the outer surface of the corresponding condyle, above the 

 attachment of the popliteus muscle, and to the upper and back part of the 

 same condyle. The fleshy fibres of the heads are united along the middle 

 line by a narrow thin aponeurosis, and terminate inferiorly with the soleus' 

 in the common tendon of insertion. 



One surface is covered by the fascia. The other is in contact with the 

 soleus and plantaris, and with the popliteal vessels and the internal popli- 

 teal nerve. The heads, by which the muscle arises, assist to form the 

 lateral boundaries of the popliteal space : and the fleshy inner head 

 descends lower than the outer. In the outer head a piece of fibro-carti- 

 lage or a sesamoid bone may exist. 



Action. When the foot is unsupported, the gastrocnemius extends the 

 ankle ; and when the toes rest on the ground, it raises the os calcis and 

 the weight of the body, as in standing on the toes, and in progression. 



Taking its fixed point at theos calcis, the muscle draws down the femur 

 so as to bend the knee joint. 



Dissection. To see the soleus, the gastrocnemius is to be reflected by 

 cutting across the remaining hea-1, and the vessels and nerves it receives. 

 After the muscle has been thrown clown, the soleus and plantaris must be 

 cleaned. 



The SOLEUS (fig. 208, B ) is a large flat muscle, which is attached to 

 both bones of the leg. It arises from the head, and the upper third or 

 half of the posterior surface of the shaft of the fibula ; from the oblique 

 line across the tibia, and from the posterior edge of this bone in the 

 middle third ; and between the bones from an aponeurotic arch over the 

 large bloodvessels. Its fibres are directed downwards to the common 

 tendon. 



The superficial part of the soleus is in contact with the wastrocnemius ; 

 and the opposed surfaces of the two are aponeurotic. Beneath the soleus 

 lie the bones of the leg, the deep layer of muscles, and the vessels and 

 nerves. 



