MUSCLES OF THE LEG. 457 



lique ridge on the posterior surface of the tibia, just at the lower 

 edge of the popliteus muscle, and from the internal angle of the 

 tibia for four or five inches. The two origins are separated for 

 the passage of the posterior tibial vessels. 



The body of this muscle has a great intermixture of tendinous 

 matter in it, and from its lower extremity proceeds another 

 origin of the tendo-achillis. About three or foftr inches above 

 the heel, this tendon joins the anterior face of the tendon of the 

 gastrocnemius, and by the union of the two the tendo-achillis 

 is completed, and then inserted into the posterior surface of the 

 os calcis near its tuberosities. The tendon becomes more round 

 as it descends. 



These muscles extend the foot, and are all-important in walk- 

 ing. A bursa is between their tendon and the os calcis. 



'The Plantaris, 



is a singular little muscle, concealed by the gastrocnemius, 

 and has a short fleshy belly and a long tendon. It arises, fleshy, 

 from the ridge of the os femoris, just above the external eon- 

 dyle, passes across the capsular ligament of the joint, and ad- 

 heres to it in its course; the belly terminates somewhat below 

 the head of the tibia, in a long, delicate tendon, which descends 

 between the inner part of the soleus and the gastrocnemius. 



At the place where the tendons of these unite, the tendon of 

 the plantaris emerges from between them, and, running at the 

 inner edge of the tendo-achillis, is inserted into the inside of the 

 os calcis, just before the insertion of the latter. 



It extends the foot. This muscle is sometimes wanting. It 

 contributes so little to the motions of the foot, and, in other re- 

 spects, is of such doubtful use, that its proper destination is un- 

 certain. In some mammiferous animals it is large and impor- 

 tant; perhaps, therefore, in the human subject, it is one of the 

 links connecting us with animals, of which there are many evi- 

 dences in the muscular system. 



The Popliteus, 



Is a triangular muscle on the back of the knee joint. It arises, 

 by a thick round tendon, from a deep depression on the exte- 

 VOL. I. 39 



