32© On Galvanifm, 



nerve be cut, and its two ends be in contact, Galvanifm. 

 takes place ; but if they are only brought near to each other, 

 without contact, it is intercepted. 



III. Among the effects refulting from the different compe- 

 titions of the exciting arc, we fhall remark the following : 

 The moft favourable compoGtion is when it conGfts of three 

 pieces, each of which is a different metal. One muft touch 

 the nerve, and the other the mufcle : thefe are called the 

 fupports, or armatures. The third forms the communication. 

 This is called the communicator. But one or two of thefe 

 may be omitted. Animal bodies, or water, may be placed 

 between them j or other fubftances, either metallic combi- 

 nations, or all other metals, &c. may be fubftituted in their 

 ftead. It has not yet been poffible to determine exactly 

 what are the moft ineffectual combinations ; but they have 

 been already claifed to a certain point, according to the de- 

 gree of their efficacy. Gold, Giver, zinc and tin, are the 

 metals moft favourable to Galvanifm, when introduced into 

 the exciting arc. 



In general a fingle metal does not act, except when all 

 other circumftances are favourable ; but in that cafe it has 

 been often feen to act. Error, however, may readily here 

 arife ; for, if one of the ends of the arc be alloyed, in a pro- 

 portion ever fo little different, the arc acts as if there were 

 two metals. By rubbing one end with a different metal, 

 fometimes even with the fingers, or by breathing upon it, 

 efficacy may be communicated to it, under circumftances 

 where it would not otherwife have poffeffed any. 



Gxydes act lefs efficacioufly, cateris paribus y than their 

 metals. Dry carbon acts as an aftual metal. It is not in- 

 tercepted by water and moift fubftances, nor by the fingers 

 if wet ; but this is not the cafe if the fingers be dry. The 

 energy of Galvanifm is not intercepted or diminifhed by 

 pieces of dead flefh. The effects of it are fenfibly checked 

 by the epidermis ; and they are incomparably greater in 



flayed 



