332 ELECTEO-PHYSIOLOGY. 



of mammifers than in those of reptiles, that they are equally obtained in nerve3 

 which have for several hours lost their excitability as in those just detached from 

 tiie living animal, I have had no hesitation in concluding that the electro-tonic 

 ^ate is an effect independent of the electro-motor power, and in general of the 

 life of the nerve. I spoke at length, in one of the former lectures, of the 

 secondary electro-motor power discovered in the nerves; a phenomenon which, 

 as I stated, the nerve presents in common with all porous solid bodies im- 

 bibed with a conducting lifjuid, and which is owing to the electric currents 

 excited between the products of electrization deposited on the nerve in contact 

 with the electrodes of the battery. I showed that in the spaces of a nervo 

 beyond the electrodes — that is, in the portions which we will call neutral, from 

 their not having been traversed by the current, there are generated nevertheless 

 currents directed exactly as is the current of the battery between the electrodes. 

 The cause of these secondary currents is also known. In contact Avith the 

 positive electrode acids are sepaiated, oxides in contact with the negative. Now, 

 as between water and an acid liquid a current is produced, directed in the liquid 

 from the water to the acid, as likewise a current is produced between water and 

 . an alkaline liquid directed in the liquid from the alkaline liquid to the Avater, 

 there is little difficulty in understanding how, in the portions of the nerve 

 beyond the electrodes, being those in which the electro-tonic state is developed, 

 secondary currents should be generated directed exactly as those Avhich charac- 

 terize that state — that is-, as the current of the battery. I will further recall 

 that these secondary currents are generated after an iustantaneous passage of 

 the battery, whence there is no wonder if, with a very delicate galvanometer, 

 the effects of the electro-tonic state should be manifested Avhen the current barely 

 begins to pass. 



I will mention in conclusion that there is in the frog, as if that animal were 

 destined by nature to a revelation of all the secrets of animal electricity, another 

 tissue endowed with strong electro-motor pov/er, namely,, the skin. Let us take 

 the skin of a frog, and, after cutting a long strip, form of this a roll or cylinder, 

 and let us cut this roll transversely at its two extremities; if the cushions of the 

 galvanometer be now brought into contact, one Avith the transverse section, the 

 other Avith the natural surface of the skin, Ave shall obtain, as Budge has observed, 

 a current directed in the galvanometer from the transverse section to the surface 

 of the skin. It is scarcely probable, however, that this current is really a fact 

 of animal electricity, and even its direction, in some sort contrary to that of 

 the muscular current, strengthens this suspicion. Perhaps to this electro-motor 

 poAver of the skin, whatever it may be, is due the opinion once entertained, that 

 the contraction obtained by Galvani in folding the leg on the nerve succeeded 

 better Avith the leer covered with skin that when denuded of it. 



Lecture VI. — Electrical fishes. — General pbeuoiik3na of the dischargo of electrical fishes. — 

 Chemical action. — Spark. — Deviation of the needle ot the gt),lvanonieter. — Directiou of the 

 discharge in various" fishes. — Structure and chemical composition of tlie organ. — Fourtli. 

 or electrical lobe. — Elementarj electro-motor organ and laws of the electrical function. — 

 Organ an electro-motor constantly charged. — Electrical phenomena of muscular coiitrac- 

 tiou. — Iuducti\e contraction. — Proofs that it is owing to a current or electric discharge 

 which arises in the act of contraction. — Experiments which prove that the contraction con- 

 sumes the electro-motor power of the muscles. — Comparison between the muscular electro- 

 motor and the electric organ. 



Arrived at the last lecture of this course, it gives me pleasure to be able to 

 illustrate in a living torpedo one of the most singular and most instructive cases 

 pertaining to the subject under consideration. 



The tislies endowed Avith the electrical function are, according to the natural- 

 ists, five or six in number ; but as it is our present object merely to giA^e, as 

 far as possible, a theory of the electrical function, we shall confine ourselves to 



