302 ELECTRO-PHYSIOLOGY. 



in the muscles after contraction, and tbat the difference does not disappear by 

 keeping the muscle in a vacuum in order to cause the carbonic acid to exhale. 



It should be further observed that the mechanical labor of the contraction is 

 not all the force which is excited iti a muscle in that act. We shall see hereafter 

 that electricity is developed. What I wish to point out here is that heat also is 

 developed in a muscle in contraction. Bequerel did not make this fact apparent, 

 because he operated on an animal entire and alive, from which it resulted that 

 in the act of contraction the blood flowed into the muscles, and to this circum- 

 stance was attributed the rise of the temperature. 



I shall place before you direct proof, derived from a frog prepared, and, there- 

 fore, without blood, of the heating of a muscle by simple contraction. I take 

 two thermo-electric pairs of bismuth and antimony so arranged that the metals 

 of the same name communicate with each other ; the two bismuths, for instance, 

 are placed in communication and the two pieces of antimony are respectively 

 united to two extremities of a galvanometer. In this arrangement, if the two 

 pairs are heated to the same temperature there is no current produced, nor devia- 

 tion in the needle ; but if one of the two pairs is a little warmer than the other, 

 there suddenly arises a current, which we call differential. It is in this way 

 only that we succeed in making quickly and satisfactorily a comparative ex- 

 periment of this kind. 



Let us return to our experiment on the frogs ; we prepare two a la galvani, 

 and into a thigh of one of them is introduced a thermo-electric pair, while the 

 other pair is placed in the thigh of the other frog. We wait till the equilibrium 

 of temperature is well established and the needle stands at zero, and then cause 

 one of the frogs to contract, at the instant the needle deviates, as if the thermo- 

 electric pair imbedded in the thigh of the frog which contracts were heated by 

 contact with a warm body. Hence the simple contraction of a muscle developes 

 heat. 



All these considerations, on which, perhaps, I have dwelt too long, conduct 

 lis necessarily to the conclusion — a very important one for the theory of electro- 

 physiological phenomena — that " the excitation of a nerve by means of a cur- 

 rent, as in the kindling of a mass of powder by a spark, gives rise in the mus- 

 cle to chemical phenomena ; that is to say, increases the so-called muscular res- 

 piration ; and it is through these chemical phenomena and the mechanical labor 

 of the contraction, taking into account also the development of heat, that we 

 verify in effect the relation demanded by the mechanical theory of heat." Thus 

 we see the important progress which this part of electro-physiology has made 

 in quite recent times. 



Since from the chemical action of the muscular respiration there is a transi- 

 tion to the contraction of the muscle, it remains to discover by what mysterious 

 concatenation this transformation is accomplished. It is certainly not my inten- 

 tion to show, by an experiment, how these things take place in the muscle, but 

 only to make it better understood in what this mystery consists. I have here a 

 large electro-dynamic spiral, in the interior of which I have suspended a piece 

 of elastic wire or spring of soft iron. This last is fixed at top, and below is 

 united to a silk thread which is wound around a very delicate pulley. Around 

 the same pulley is wound in the contrary direction a silk thread, bearing a 

 weight which stretches the elastic wire to a certain point. Lastly, to the axis 

 of the pulley is attached a long index of ivory or straw. Every time that an 

 electric current passes in the spiral, the elastic iron wire is shortened, its coils 

 approach one another, and the index manifests the raising of the weight ; when 

 the electric current ceases the weight sinks, and the index moves in the oppo- 

 site direction. It is precisely the same alternation which you have witnessed 

 in the case of a muscle suspended in the dynamometer when the current begins 

 to act and when it ceases. In the experiment which I now exhibit the current 

 of th-; spiral magnetizes the coil of iron wire, and the constituent parts thus 



