BACK OF THE LEG. 241 



DISSECTION XII. 



BACK OF THE LEG. 



The dissection of the back of the leg is to be commenced by an in- 

 cision from the popliteal space to the heel. The integument is to be 

 reflected with care, as there are several superficial structures to be 

 examined. 



The external saphena vein, commencing on the outer 

 border of the foot, ascends along the outside of the tendo 

 Achillis, upon the belly of the gastrocnemius muscle and 

 between its two heads, to the popliteal space, where it 

 enters the popliteal vein. 



The external saphena nerve, formed from the communi- 

 cans peronei and poplitei, which unite at a variable distance 

 down the leg, or occasionally, in the case of their non-union, 

 iing one of these nerves itself, lies at the side of the ex- 

 jrnal saphena vein along the outer border of the tendo 

 .chillis ; it curves around the external malleolus and is 

 Listributed to the outer border of the foot and little toe. 

 The muscles of the leg are arranged in two layers, super- 

 nal and deep; the superficial layer constitutes the "calf 

 the leg." 



The GASTROCNEMIUS MUSCLE, the first muscle of the 

 superficial layer, arises by two heads, of which the inner 

 is the larger, from the surface of bone above each condyle 

 of the femur ; these heads converge and form the lower 

 boundary of the popliteal space, and are situated inside 

 the tendons forming the ham-strings ; they are each sup- 

 plied with an arterial branch, the sural, from the popliteal 

 artery. The large muscular belly of the gastrocnemius 

 terminates in a brilliant aponeurosis, finally converted into 

 a -large, round tendon, called the tendo Achillis, which is 

 inserted into the lower part of the posterior surface of the 

 os calcis ; this tendon, for some distance above its insertion, 

 is common to this muscle and to the soleus which lies be- 

 neath it. 



The small rounded tendon of the plantaris muscle, running along 

 the inside of the tendo Achillis, to which it is more or less adherent, 

 should be sought for and isolated, that it may not be cut across iu 

 dividing the gastrocnemius. 



The gastrocnemius should be separated along its borders from the 

 soleus, in order to determine the line of division between them ; H 

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