MUSCULAR CONTRACTIONS. 



PRODUCTION OF MUSCULAR CONTRACTIONS. When any part 

 of an animal, either still living or recently killed, is made to form 

 part of a voltaic current, a shock is experienced, closely resem- 

 bling that caused hy a weakly-charged Leyden jar, and the 

 intervening muscles are thrown into convulsive action. This 

 effect is equally produced whether the current be applied to the 

 motor nerves themselves, or to the central organs of the nervous 

 system. Thus, if while the negative pole is touched by the fin- 

 gers of one hand, the other be brought into contact with the 

 positive end of a battery, a concussion will be felt in both hands, 

 which will extend to the wrists, the elbows, or even the chest, 

 according to the intensity of the developed electricities. And it 

 is further to be remarked, that not only is this shock felt when 

 the circuit is completed, but also at the instant when it is broken, 

 while during the maintenance of the circuit, no such effect is 

 perceived. In order, however, to the production of these pheno- 

 mena, it is necessary that the circuit be completed or interrupted 

 with rapidity ; for if the electric current be gradually admitted 

 into, or withdrawn from, the body of an animal, no spasms will 

 ensue. This fact is interesting, and in a practical point of view 

 should be borne in mind, as will be seen when we come to 

 treat of the remedial application of Galvanism and Electro- 

 Magnetism. 



From the experiments of various physiologists, it would seem 

 that the effect of the voltaic current is more powerful on the 

 voluntary than on the involuntary muscles. The muscles of the 

 animal body may, it is well known, be divided into three classes : 

 the voluntary, the involuntary, and those of a mixed charac- 

 ter. The muscles which move the limbs are voluntary ; the 

 heart is an involuntary muscle ; and the diaphragm may be cited 

 as an organ of the mixed class. Now, upon all three the galva- 

 nic current exercises a similar power, that is, it stimulates them 

 to convulsive action. The involuntary muscles are doubtless 

 much less affected by it than those which are influenced by the 

 will ; and it has even been contended by some that they are 

 entirely exempt from its influence. This opinion, however, has 

 been most satisfactorily refuted by the experiments of Fowler, 



