CHAPTER XL 

 ELECTRO-PHYSIOLOGY. 



A LITTLE more than a hundred years ago the foundation both of 

 electro-physiology and of the vast science of voltaic electricity was 

 laid by a chance observation of a professor of anatomy in an Italian 

 garden. It is indeed true that long before this electrical fishes were 

 not only popularly known, but the shock of the torpedo had been to 

 a certain extent scientifically studied. But it was with the discovery 

 of Galvani of Bologna that the epoch of fruitful work in electro- 

 physiology began. Engaged in experiments on the effect of static 

 and atmospheric electricity in stimulating animal tissues, he hap- 

 pened one day to notice that some frogs' legs, suspended by copper 

 hooks on an iron railing, twitched whenever the wind brought them 

 into contact with one of the bars (p. 651). He concluded that 

 electrical charges were developed in the animal tissues themselves, 

 and discharged when the circuit was completed. Volta, professor of 

 physics at Pavia, fixing his attention on the fact that in Galvani's 

 experiment the metallic part of the circuit was composed of two 

 metals, maintained that the contact of these was the real origin of 

 the current, and that the tissues served merely as moist conductors 

 to complete the circuit ; and after a controversy lasting for more than 

 a decade, he finally clinched his argument by constructing the voltaic 

 pile, a series of copper and zinc discs, every two pairs of which were 

 separated by a disc of wet cloth. The pile yielded a continuous 

 current of electricity. ' So,' said Volta, ' it is clear that the tissue 

 in Galvani's experiment only acts the part of the cloth.' Galvani, 

 however, had shown in the meantime that contraction without metals 

 could be obtained by dropping the nerve of a preparation on to the 

 muscle (p. 651); and it soon began to be recognised that both 

 Galvani and Volta were in part right, that two brilliant discoveries 

 had been made instead of one ; in short, that the tissues produce 

 electricity, and that the contact of different metals does so too. 

 Although it is curious to note how completely the growth of that science 

 of which Volta's discovery was the germ has overshadowed the parent 

 tree planted by the hand of Galvani, yet animal electricity has been 

 deeply studied by a large number of observers, and many interesting 

 and important facts have been brought to light. 



