280 INFERIOR EXTREMITY 



from the posterior aspect of the distal end of the femur. These 

 heads have been already studied in connection with the pop- 

 liteal space, which they bound in its distal part. The lateral 

 head springs from an impression on the lateral surface of the 

 lateral condyle of the femur, and also from a small portion of 

 the popliteal surface of the bone immediately proximal to the 

 condyle. The medial head takes origin from the proximal part 

 of the medial condyle, and likewise from a rough ridge on 

 the adjacent part of the planum popliteum. The two 

 fleshy bellies swell out as they descend, and end, near the 

 middle of the leg, in a thin aponeurotic tendon. They 

 do not blend with each other. They are usually separated by 

 a furrow, at the bottom of which the flattened tendon, 

 to which the fasciculi of both heads are attached, may be 

 seen. The medial head is the more bulky of the two, and 

 it extends more distally than the lateral head. The flattened 

 tendon in which they terminate narrows slightly as it descends, 

 and, a short distance distal to the middle of the leg, it blends 

 with the stouter tendon of the soleus to form the tendo 

 calcaneus (Achillis). 



The gastrocnemius is supplied by the tibial nerve. 



Dissection. The medial head of the gastrocnemius may be divided 

 at the level of the knee-joint. The sural arteries from the popliteal 

 trunk, and the branches of supply from the tibial nerve which 

 enter the heads of the gastrocnemius, can thus be preserved. On rais- 

 ing the proximal portion of the medial head, a bursa which intervenes 

 between it and the condyle of the femur will be brought into view. On 

 opening this with the knife it will, in all probability, be found to com- 

 municate with the interior of the knee-joint. The smooth and tendinous 

 opposed surfaces of the gastrocnemius and the soleus, and the narrow tendon 

 of the plantaris, which passes distally and medially between them, are 

 displayed when the medial head of the gastrocnemius is drawn aside. 



M. Plantaris. The small fleshy belly of the plantaris is not 

 more than three or four inches long. It lies along the medial 

 side, and partly under cover of the lateral head of the gastro- 

 cnemius, and it arises from the popliteal surface of the femur 

 immediately proximal to the lateral condyle. It ends in a 

 slender tendon which is remarkable for its great length. This 

 proceeds distally and medially, between the gastrocnemius 

 and soleus, and then runs along the medial side of the tendo 

 calcaneus (Achillis) to gain insertion into the posterior aspect 

 of the calcaneus. It is frequently closely connected with 

 the tendo calcaneus, and sometimes becomes blended with 



