MYOLOGY 227 



Muscles of the Posterior Region 



It will not be unprofitable to recall to mind that, in man, 

 the muscles of this region are arranged in two layers : 

 a superficial layer consisting of the gastrocnemius and 

 soleus, to which is added a muscle of Uttle importance, 

 the plantaris, and a deep layer formed by four muscles — 

 the popliteus, flexor longus digitorum, tibiahs posticus, 

 and flexor longus pollicis. 



The gastrocnemius and soleus, independent in their upper 

 portion, unite below in a common tendon ; they thus 

 form also a triceps muscle, which we designate under the 

 name of the triceps of the leg, or triceps suralis, because 

 it forms the elevation of the calf of the leg (from sura, 

 calf). 



Gastrocnemius (Fig. 83, 9, 11 ; Fig. 84, 13, 14 ; Fig. 86, 

 7, 9 ; Fig. 88, 13). — The external and internal heads of 

 the gastrocnemius, distinct from one another only in their 

 upper portion, arise from the shaft of the femur, above 

 the condyles, on the borders of the popUteal surface, to a 

 relatively considerable extent in the great quadrupeds. 



At this level they are situated in the popliteal region — 

 that is to say, in the space limited externally by the biceps, 

 and internally by the semi-tendinosus. But as they descend 

 to a rather low level on the leg in quadrupeds, and especially 

 in carnivora, they do not, properly speaking, determine a 

 projection of the calf of the leg. However, they pass from 

 this region but to be soon continued b}/ a tendon — the tendo- 

 Achillis, which is inserted into the calcaneum. 



Now, the region of the tarsus is called by veterinarians the 

 ham, the posterior surface of which is angular, because of 

 the oblique direction of the leg with regard to the vertical 

 direction of the metatarsus and the presence of the 

 calcaneum ; the prominence which this surface presents has 

 received the name of the point of the ham, and the tendon 

 which ends there that of the cord of the ham. 



But the tendo-Achillis does not alone form this cord. 

 Indeed, as we will soon see, the tendon of the superficial 

 flexor of the toes takes part in its formation. 



15—2 



