200 



PHYSIOLOGY OF MUSCLES AND NERVES. 



surface of which (turned toward the bone of the lower 

 leg) is formed solely of muscle-fibres, exhibiting a delicate 

 longitudinal streak as the only indication of the tendon 

 buried within it ; the arched dorsal surface is, on the 

 contrary, clothed, as regards the lower two-thirds of its 

 length, with tendonous substance which passes below 

 into the so-called tendo Achillis. 



It is evident that such a muscle has naturally an' 

 oblique cross-section, represented by this tendonous 

 covering, and a longitudinal section which includes the 

 whole of the flat, and a little of the curved portion. 

 This muscle can, therefore, without any further pre- 



FiG. 54. The cuuhents of a gastrocnemius. 



paration afford currents ; for which reason it may be 

 most advantageously used in a large number of experi- 

 ments. 



Eegarding once more the structure of the gastro- 

 cnemiiis, as it has just been described, a natural longitu- 

 dinal section is recognisable in the whole flat part and 

 a little of the upper portion of the curved surface ; and 

 a natural cross- section is to be recognised in the greater 

 and lower part of the curved upper surface. No second 

 cross-section exists in this muscle, for the upper tendon 

 is buried within the muscle. The currents which the 

 muscle sends through an arch applied so as to connect 



