370 THE INFERIOR EXTREMITY 



plantar flexion it cannot flex the knee, and if the knee is 

 flexed it cannot act upon the ankle. It is important to 

 remember these facts in association with fractures of the 

 distal part of the femur. 



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. 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. The 

 tendon proceeds distally and medially, between the gastro- 

 cnemius 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 

 it, or with the fascia of the leg above the level of calcaneus. 



The plantaris is supplied by a branch from the tibial nerve. 

 Its actions are similar to those of the gastrocnemius. 



Dissection. Divide the lateral head of the gastrocnemius, 

 at the level of the knee joint. Turn the proximal part upwards, 

 and examine it to see if it contains a sesamoid bone which is 

 sometimes present (Fig. 185) ; then look for a bursa which is 

 occasionally present between it and the posterior part of the 

 capsule of the knee joint. Turn the distal part downwards and 

 note the manner in which the two heads join their thin aponeuro- 

 tic tendon, and the union of the tendon with the tendon of the 

 soleus to form the tendo calcaneus. Now clean the posterior 

 surface of the soleus, note its origin from (i) the back of the 

 head, and the proximal part of the posterior surface of the body 

 of the fibula, (2) the fibrous arch over the distal end of the popliteal 

 artery, (3) the oblique line of the tibia, and (4) the middle 

 third of the medial border of the tibia. Note also the manner 

 in which the majority of its fibres end in the strong tendon which 

 blends with the tendon of the gastrocnemius to form the tendo 

 cakaneus, whilst some of them pass directly to the deep surface 

 of the tendo calcaneus. 



M. Soleus. The soleus is a flat, thick, and powerful 

 muscle which arises from both bones of the leg, as well as 

 from a strong fibrous arch which is thrown across the popliteal 

 vessels. Its fibular origin is from the posterior surface of 

 the head and the proximal third of the posterior surface 

 of the body of the bone ; by its tibial origin it is attached to 

 the linea poplitea of the tibia, distal to the popliteal surface, 

 and, more distally, to the medial border of the bone as far 

 as the middle of the leg (Fig. 166, p. 376). The soleus ends 



