i62 GREAT MEN OF SCIENCE 



which remained to be discovered. His chief discovery was 

 the fact that the strength of the contractions depended upon 

 the choice of the two metals, which must touch one another, 

 while one of them also touches the nerve, and the other 

 the muscle; but he also found that the contraction became 

 weaker and somewhat uncertain, but did not quite vanish, 

 when a bow of one single uniform metal was interposed 

 between nerve and muscle. This latter observation, which he 

 made frequently, and always with the same result, led him 

 finally to regard the animal preparation itself as the source of 

 the electricity which caused the contraction. Nerve and 

 muscle together thus appeared like a Leyden jar able to 

 charge itself, which was discharged when its two coatings 

 were connected together. 'Animal electricity' had been 

 discovered. 



In the fourth part, entitled 'Some Suppositions and Con- 

 clusions,' Galvani attempts to offer some hints, particularly 

 for medicine, as the result of his work. He is here very 

 modest in his statement: 'But all this I have thought out, as 

 I have said, in order that it may be considered by the great 

 and learned ... in order that they may some day make use of 

 it; that was our main desire' - as he also says in the intro- 

 duction to the whole: 'For eminent men of learning will be 

 put in a position through reading this essay to develop these 

 results themselves further by consideration and experiment 

 and above all to reach that goal towards which we have 

 striven, but from which we are perhaps still very far.' 



Galvani's wish soon reached fulfilment after the appear- 

 ance of his essay in one direction at least, and in a peculiar 

 way, since Volta took up the study of frog preparations just 

 as Galvani had prepared the way so extensively. He started 

 mainly from the observation of Galvani, that the contraction 

 was more lively when two suitable and different metals were 

 used in the circuit. The endless riches of nature presented 

 him with an entirely new and unexpected discovery; that the 



