ANIMAL ELECTRICITY ' 



561 



tissue (Fig. 297). The current of injury can be simply demonstrated 

 by Galvani's experiment already quoted. It may also be shown in 

 nerve by placing the cut surface of the nerve on one plug of kaolin 

 ^nd the uninjured part on another. Then, if the attached muscles be 

 sufficiently excitable, on bringing the kaolin plugs into contact with 

 strong saline, which is a good conductor of electricity, the muscles 

 contract (Fig. 298). 



-DIAGRAM OF THE EXPERIMENT TO SHOW THE STIMULATION OF A NERVB 

 BY ITS OWN " CURRENT OF INJUKY." 



FIG. 299. DIAGRAM OF THE EXPERIMENT ON SECONDARY TWITCH. 



FIG 300 DIAGRAM OF THE EXPERIMENT TO SHOW THE STIMULATION OF A MUSCLB 

 BY THE " CURRENT OF ACTION " OF ANOTHER MUSCLE. 



A similar condition pertains when any part of a muscle or nerve 

 is more active than the rest. The active part in reference to the 

 current through the galvanometer is negative to the resting part. 

 Such a current is termed the " current of action." It may be simply 

 .shown by laying two nerve-muscle preparations, A and B, upon a 

 glass plate, and placing the nerve of one muscle (A) along the other 

 muscle (B). Upon exciting the nerve of B, the muscle contracts, 

 followed immediately by a contraction [of A. Similarly, if B fco 



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