On Galvanifm. 3 21 



flayed animals, or in parts of the human body from which 

 the epidermis has been removed. 



It cannot be faid that Galvanifm is intercepted by all idio- 

 electric bodies ; but, on the other hand, it is intercepted by 

 all fubitances which are itrong conductors of electricity. 

 Such are flame, very dry animal bones, the fteam of water, 

 glafs brough to a red heat, &c. 



IV. Galvanifm is influenced alfo by feveral circumftances 

 foreign to the compofition of the two arcs- Such as, i. The 

 ftate of the parts which are fubjected to the operation : the 

 fremer they are, the flronger are the effects. 2. The longer 

 or fhorter exercife of Galvanifm : fufceptibility of Galva- 

 nifm is in general excited by exercifmg it; is exhaufted by 

 continuance, and renewed by repofe. 3. The fucceflion of 

 various experiments. A difpofition of metals which at firft 

 had been ineffectual, has become effectual after a different 

 dipt fi f ion. Two uncertain experiments are hurtful to each 

 other, and become (till more fo if made in fucceflion. 

 4. ihe ftate of the atmofphere. The atmofphere electric; 

 the animal on which the operation is performed charged 

 and infulated, the effect: is the fame. The whole apparatus 

 placed under water, the effect remains the fame. 



V. There are vaiious artificial means to wcuken or revive 

 the fufceptibility of Galvanifm. Thus, a frog exhaufted and 

 brought near to a charged elertrophorus refumed its fufcep-. 

 tibility. Alcohol, on the other hand, weakens and even ex- 

 tinguishes it fo as never to return. Potafh produces the 

 fame effect, only flowly. According to M. de Humboldt, 

 this fufceptibility is in many cafes reftored by oxygenated 

 muriatic acid gas. The commiflioners did not obferve this 

 cincumlhmce ; but they propofe to refume the fubject, and to 

 repeat feveral other experiments of that learned philofopher. 



They have already repeated thofe on the action of Galva- 

 nifm on the heart, and have obferved, as he did, that its 

 action is the fame as on the voluntary mufclvs, and that it 

 accelerates their movement. 



Vol. I. Y XIX Of 



