LUIGI GALVANI i6i 



without reference to the observations contained in the first 

 part. 



In the second part, Galvani investigates the action of 

 atmospheric electricity on animal preparations. In these 

 experiments, which were carried out in the open air, he 

 found very powerful muscular contractions taking place at 

 every flash of lightning. Here, as in the first part, the frog 

 preparation only acted as a highly sensitive detector of electric 

 forces. This part does not bring anything new, in so far as 

 the electrical charges of thunderclouds had at that time been 

 already sufficiently proved by the bringing down of sparks 

 (as in Frankhn's experiments with kites in 1652); this part is 

 only short. 



The position is different as regards the third part. This 

 starts from an entirely new observation. For the experi- 

 ments of the first and second part it had always been 

 necessary to attach conductors - wires or other metal parts - 

 to both the nerves and the muscles of the frog preparation, 

 and Galvani noticed in experiments carried out in the open 

 air, that contractions occurred even under a clear sky, 

 when metallic parts of different nature touched one another; 

 when, for example, the nerve of the preparation was attached 

 by means of a brass hook to an iron garden fence, and the 

 muscle touched the iron. Galvani thought at first that these 

 contractions were to be referred to changes in atmospheric 

 electricity, 'but when I then carried the animal into a closed 

 room, laid it on an iron plate, and began to press upon the 

 latter the hook attached to the spinal cord, behold, the same 

 contractions, the same motions.' Thus a new discovery was 

 made. It again challenged Galvani to an extraordinary 

 number of fresh experiments, whereby he changed the 

 conditions in all sorts of ways, in order to discover the 

 essential point, but every time entirely without the assistance 

 of any hitherto known source of electricity, for it was obvious 

 that a new source of electricity had been found, the seat of 

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