MUSCLES ON THE LEG. 



389 



both gastrocnemii unite, and form a strong round cord, which 

 is called tendo-Achillis. 



Inserted into the upper and posterior part of the os caleis, by 

 Fig. 104.* the projection of which the tendo-Achillis is 

 placed at a considerable distance from the 

 tibia. 



Use. To extend the foot, by bringing it 

 backwards and downwards. 



3. Plantaris. 



Arises, thin and fleshy, from the upper 

 and back part of the root of the external 

 condyle of the os femoris, near the interior 

 extremity of that bone, adhering to the liga- 

 . ment that involves the joint in its descent. 

 It passes along the second origin of the 

 soleus and under the gemellus, where it 

 sends off a long, slender, thin tendon, which 

 comes from between the great extensors, 

 where they join tendons ; then runs down 

 by the inside of the tendo-Achillis. 



Inserted, into the inside of the posterior 

 part of the os caleis, below the tendo- 

 Achillis. 



Use. To assist the former, and to pull the 

 capsular ligament of the knee from between 

 the bones. It seems likewise to assist in rolling the foot 

 forwards, 



* The deep layer of muscles of the posterior libial region. 1. The lower 

 extremity of the femur. 2. The ligamentum posticum Winslowii. 3. The 

 tendon of the semi-membranosus muscle dividing into its three slips. 4. The 

 internal lateral ligament of the knee-joint. 5. The external lateral ligament. 

 0. The popliteus muscle. 7. The flexor longus digitorum. 8. The tibialis 

 posticus. 9. The flexor longus pollicis. 10. The peroneus longus muscle. 

 11. The peroneus brevis. 12. The tendo-Achillis divided at its insertion into 

 the os caleis. 13. The tendons of the tibialis posticus and flexor longus digito- 

 rum muscles, just as they are about to pass beneath the internal annular liga- 

 ment of the ankle ; the interval between the latter tendon and the tendon of 

 the flexor longus pollicis is occupied by the posterior tibial vessels and nerves. 



33* 



