ELECTRIC PHENOMENA OF MUSCLE. 445 



series of springs, the various skeletal muscles being so arranged 

 as to stretch others by their contraction. When one muscle for 

 example, the biceps contracts, it finds an elastic antagonist 

 already tense; this it has to stretch as it shortens. The triceps 

 thus acts as a weak spring, opposing the biceps, and it gently returns 

 to its natural length when the contraction of the biceps ceases. 

 By their mere elasticity the muscles are kept tense and ready for 

 action, and have to act against a gentle spring-like resistance, so 

 that the motions are even, and there is no jerking, as would occur 



FIG. 181. 





Non-polarizable Electrodes. The glass tubes (a a) contain sulphate of 

 zinc solution (z. s), into which well amalgamated zinc rods dip. The lower 

 extremity is plugged with china clay (ch. c), which protrudes at (c') the point. 

 The tubes can be moved in the holders (h h), so as to be brought accurately 

 into contact with the muscle. (Foster.) 



if the attachments of the inactive muscles were allowed to become 

 slack. 



Electric Phenomena. In a living muscle electric currents may 

 be detected, having a definite direction, and certain relations to 

 the vitality of the tissue. As they seem to be invariably present 

 in a passive muscle, they have been called natural muscle- cur rents. 



They are generally studied in the muscles of cold-blooded ani- 

 mals after removal from the body. The muscle is spoken of as if 

 it were a cylinder with longitudinal and transverse surfaces cor- 

 responding to its natural surface and its cut extremities. In such 



