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XII. Electro-Physiological Researches. — Second Memoir, On the proper Current of the 

 Frog. By Signor Carlo Matteucci, Professor in the University of Pisa, 8^c. 8^c. 

 Communicated by Michael Faraday, Esq., F.R.S., ^c. ^c. 



Received May 7, — Read June 19, 1845. 



In the seventh chapter of my Traits des Ph^nom^nes Electro-Physiologiques des 

 Animaux, after having examined all that Galvani, Humboldt, Valli, and more 

 recently Nobili, have said on this subject, I mentioned all my own researches from 

 which the laws of this phenomenon follow. Comparing the muscular and the proper 

 current together, we find that the influence of the different circumstances affects both 

 currents equally. Thus it is that both the muscular and the proper current vary in 

 the same sense with the variation of the temperature of the medium in which the 

 frogs live. Sulphuretted hydrogen diminishes the proper current just as it does 

 the muscular current. The same may be said of the effects produced upon the 

 proper current by the different degrees of activity of the respiration and of the circu- 

 lation of the blood. I shall not here mention all the numbers obtained in the expe- 

 riments recently performed upon the proper current of the frog. I will merely say 

 that I followed up every one of the experiments on the muscular current referred to 

 in this memoir, with another experiment on the proper current, composing the pile 

 with the legs which remained after having prepared the frogs for the muscular cur- 

 rent. After so great a number of facts, I do not hesitate in repeating what I have 

 said in page 127 of my Treatise : " comparing one with the other the circumstances 

 which exert an influence over the muscular and over the proper current, they may be 

 said entirely to resemble one another, and that that which increases or weakens the 

 intensity of one of these currents, produces the same effect upon the other." Two 

 points, however, still remain to be cleared up. Do the circumstances which affect 

 these two currents operate upon both in a like degree ? or in other words, does that 

 circumstance which diminishes as well the muscular as the proper current of the frog, 

 act proportionally in that diminution ? 



I had found in my first experiments, that comparing two piles, one consisting of 

 half thighs of frogs, the other of entire or halves of frogs, so as to obtain the proper 

 current, the signs produced by the latter pile continued longer than those evinced by 

 the muscular pile. 



I then began to renew my former experiments for the purpose of convincing myself 

 of the reality of this difference, the only one between the muscular and the proper 

 current. 



Studying afresh the influence of the various circumstances (temperature, respira- 



