556 PHILOSOPHICAL TRANSACTIONS. [aNNO 1795, 



its friability not very fit for the experiment, may yet be rendered capable by the 

 same means of producing contractions, without the assistance of any of the 

 metals. 



My next and last object is to inquire, whether the influence, which in all 

 these experiments immediately excites the muscles to act, be electrical or not. 

 The points of difference between any 2 species of natural bodies, even those 

 which, from the similarity of some of their most obvious qualities, have once 

 been thought the same, are found, on accurate examination, greatly to exceed 

 in number those of their agreement. When therefore 2 substances are known 

 to have many properties in common, while their differences are few, and none 

 of these absolutely contradict such a conclusion, we infer with considerable con- 

 fidence, that they are the same, though we may not be immediately able to ex- 

 plain why their resemblance is not complete. After Mr. Walsh, for instance, 

 had discovered, that the influence of the torpedo was transmitted by all the 

 various bodies which are good conductors of the electric fluid, philosophers made 

 little nesitation in admitting them to be one and the same substance, though 

 some of their apparent differences could not then be accounted for. In like 

 manner, the inquirers into the nature of the influence, the effects of which are 

 so evident in Galvani's experiments, have very generally, and in my opinion 

 justly, allowed it to be electrical, on the ground that its conductors and those 

 of electricity are altogether the same. To this however an objection has been 

 made by Dr. Fowler, which, if well founded, would certainly prove them to be 

 different substances; for he has asserted that charcoal, which is so good a con- 

 ductor of electricity, refuses to transmit the influence on which the motions in 

 Galvani's experiments depend. In reply I shall only say, that Dr. Fowler must 

 have been unfortunate with respect to the charcoal he employed, since all the 

 pieces I ever tried, and those were not a few, were found to conduct this in- 

 fluence. 



Other arguments have also been urged against the identity of the 2 influences; 

 all of which however, excepting one, I shall decline discussing, as they either 

 are of little importance, or have not been stated with sufficient precision. The 

 objection I mean is, that in none of the experiments with animals, prepared after 

 Galvani's manner, are those appearances of attraction and repulsion to be ob- 

 served, which are held to be the tests of the presence of electricity. My answer 

 to it is, that no such appearances can occur in Galvani's experiments, consistently 

 with the known requisites for their success, and the established laws of electri- 

 city. For, as it has been proved that there is naturally no disengaged electric 

 fluid in the nerves and muscles of animals, I except the torpedo and a few others, 

 no signs of attraction and repulsion can be looked for in those substances, before 

 the application of metals or charcoal ; and after these have been applied, the 



