ELECTRO-PHYSIOLOGY. 313 



theory, an explanation of the electro-physiological phenomena which arise at the 

 opening of the circuit, and has thus laid a foundation for the most important 

 progress recently made in electro-physiology. The frog which I exhibit is pre- 

 pared as usual and has been subjected to the passage of the current. I open 

 the circuit, and on the instant the member traversed by the inverse current is 

 attacked by the tetanic contraction. It may be shown by a very clear experiment 

 that this contraction depends on a particular state into which the lumbar nerve 

 has been thrown by the passage of the inverse current. In effect, if I interrupt 

 the circuit by cutting this nerve at the point of its exit from the spine, the 

 tetanic contraction ensues as usual, while it fails entirely if the nerve be cut 

 precisely at its entrance into the muscles. But in Avhat consists this particular 

 state of the nerve ? It is to this question that a recent physical discovery fur- 

 nishes an answer. 



We know what secondary polarity is, and I have before said that it is devel- 

 oped in the nervous fibres as in any moist conductor, such as is afforded by a 

 strip of paper or of flannel imbued with a saline solution. Let us observe now 

 the ])rincipal experiment. I take the sciatic nerve of a fowl, place it upon a 

 handle of gutta-percha and convey it to the galvanometer ; after having ascer- 

 tained, by touching with the extremities of the galvanometer two points in the 

 surface of this large nerve, that there is no sign therein of a current, I deposit 

 the nerve on the tv/o electrodes of platina or of moistened paper of a battery of 

 eight or ten elements of Grove. I cause the current to pass for several minutes, 

 and then return with the nerve to the galvanometer. I now obtain a very strong 

 current in a direction opposite to that of the battery, and which, according to all 

 analogy, is a current due to secondary polarity. In effect, this current is mani- 

 fested in a nerve deprived of life for many hours or even several days, as in the 

 nerve taken in the living animal ; it is manifested in a wet string, the stalk of a 

 green plant, or any solid body imbued with a liquid. 



The passage of the current collects hydrogen and the bases at the points 

 touched by the negative pole, oxygen and acids at the points touched by the 

 positive pole. These products of electrization are gradually diffused through 

 the moist solid body, and transform it through its whole length into a secondary 

 electro-motor. It may be shown, indeed, that in a fowl v/hich has been prepared 

 precisely like the frog, reduced, namely, to the pelvis, a piece of spine, the two 

 large lumbar nerves, and the legs, and which has been traversed by the current 

 from one leg to the other, the two nerves have acquired the secondary electro- 

 motor power, without having been touched directly by the electrodes of the 

 battery. 



After having discovered the secondary electro-motive property in the nerves, 

 I have also ascertained that this has not the same intensity at all points, and 

 that the portion of the nerve placed near the positive pole, and in which the cur- 

 rent enters, has acquired this property in a much stronger degree than the 

 portion situated near the negative pole. This experiment also may be easily 

 shown. I take the nerve after it has been subjected to the passage of the cur- 

 rent, cut it in half, and reverse the position of one of the halves, reproducing 

 the piece of nerve as before. As we know that the nerve has become, by the 

 passage of the current at all its points, an electro-motor, the operation I have 

 performed would be the same as if I had ten pairs of Volta, all in series, and 

 then opened the battery in the middle by reversing five of these pairs, and re- 

 established the communication by replacing two zincs and two coppers together. 

 Thus Ave have two opposite half batteries, whence, if the pairs have all the same 

 electro-motive force, the two batteries are neutralized. But if one of the batteries 

 is the stronger, we at once obtain the differential current, that is, a current due 

 to the excess of the stronger battery. In like manner, if those two portions of 

 the nerve which the current has converted into a secondary electro-motor have 

 not the same force, I shall at once perceive it after having performed the division 



m. 



