IRRITABILITY OF MUSCLES 31 



veniently produced by means of so-called induction. 

 Let us take two coils of silk-covered copper wire and 

 attach the two ends of one of these to a muscle. An 

 electric current from a battery must now be passed 

 through the other coil A. The two coils being com- 

 pletely isolated from each other, the current passing 

 through A can in no way enter into B or into the muscle 

 attached to B. If, however, the electric current in A is 

 suddenly interrupted, an electric shock immediately 

 arises in B, a so-called inductive shock ; and this passes 

 through and irritates the muscle ; that is to say, a 



Fig. 10. Induction coil. 



The coil A is connected with the batterj' by means of the \\ires x and y ; the other 

 coil, B, is connected with the muscle by means of wires fixed at q and p. 



sudden contraction of the muscle is observable at the 

 instant of the opening of the current in coil A ; and 

 this suddenly lifts the disc attached to the muscle. 

 The same thinof occurs when the current in the coil A 

 is again closed ; so that this electric irritant affords an 

 easy and simple means of causing this sudden con- 

 traction of the muscle at pleasure. This contraction 

 may be called a 'pulsation i and it will be perceived 

 from the description of the above experiments that a 

 simple electric shock, such as is afforded by the dis- 

 charge of a Kleistian jar, or any similar inductive 

 shock, is the most convenient means of producing such 

 a pulsation as often as it is required. 



