CHAPTER XI 

 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. 738). He concluded that 

 electrical charges were developed in the animal tissues themselves, 

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

 physics at Pa via, 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, or paper moistened with salt 

 solution. 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. 738) ; 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. 



Since it is in muscle and nerve that the phenomena of electro- 

 physiology are seen in their simplest expression, and have been 

 chiefly studied, we shall develop the fundamental laws with 



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