THE LEG 



369 



Adductor 

 magnus 



plantaris, and the soleus. The gastrocnemius is the most 

 superficial ; the soleus is placed under cover of the gastro- 

 cnemius ; whilst the slender plantaris extends distally and 

 medially between them. The tendons of insertion of the 

 gastrocnemius and soleus unite to form the tendo calcaneus 

 (tendo Achillis). 



M. Gastrocnemius. The gastrocnemius is a strong muscle. 

 It arises, by two heads, from the posterior part of the distal end 

 of the femur. Both heads have been already studied in 

 connection with the popliteal fossa, 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 area of the 

 bone, immediately proximal 

 to the lateral condyle. 

 The medial head takes Medialhead 

 origin from the proximal ofgastro- 



c , ,. , cnemius 



part of the medial con- 

 dyle, and also from a rough 

 ridge on the adjacent part 

 of the popliteal surface of 

 the femur. The two fleshy 

 bellies swell out as they 

 pass distally, and end, near 

 the middle of the leg, in a 

 thin aponeurotic tendon. 

 They do not blend with 

 each other, and 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 further 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 (tendo 

 Achillis). 



The gastrocnemius is supplied by the tibial nerve. It is 

 a plantar flexor of the foot and a flexor of the knee, but it 

 cannot act efficiently both on the knee and the ankle joint at 

 the same time. Therefore, if the foot is in the position of 



VOL. i 24 



Posterior cruciate 

 ligament 



Anterior cruciate 

 ligament 



FIG. 162. Posterior aspect of distal por- 

 tion of Femur, with Attachments of 

 Muscles mapped out. 



