ELECTRO-PHYSIOLOGY. 331 



motor. Nor do we better understand why, with the enfeeblement of the vital 

 force, the half thigh loses so much more than the gastrocnemiau. I repeat, tliat 

 as long as the form of the electro-motor is not known to us we shall not succeed 

 in clearing up these peculiarities which have at present the appearance of 

 anomalies. * 



Du Bois Reymond has imagined a scheme or figure for the electro-motor 

 element, comparing it to a cylinder of zinc Avhose bases are of copper. A series 

 of these cylinders immersed in an acid liquid would produce, by dipping the 

 extremities of the galvanometer in difterent points of the liquid, direct currents 

 such as are obtained from different points of the muscle; but this analogy is 

 wholly imaginary. The explanation of muscular electricity proposed some 

 years since by Liebig, who surmised that there were in tlie muscles acid liquids 

 and alkaline liquids which react, has not borne the test of experiment. 



I will not conclude this lecture without very briefly noticing the results 

 obtained in seeking whether other organic tissues have the electric properties of 

 the muscles. By introducing the platina extremities of a good galvanometer 

 into the fruit, leaves, or stalk of a plant, electric currents are obtained. Admitting 

 that these currents are constant and independent of the polarity and heterogeneity 

 of those extremities, the most probable explanation of the currents iu question 

 points at present to liquids of a different chemical nature which, with great pro- 

 bability, exist in the various parts of the plant and which react on one another. 

 Investigations of this kind have been directed to the tendons, the tissues of the 

 lungs and liver and kidneys, of animals living or recently killed, and careful 

 experiment has shown that these tissues have no proper electro-motor power. 

 This power, however, exists in the nerves, and since it is much weaker there 

 than in the muscles, (perhaps about one-eighth or one-tenth,) Du Bois Eeymond, 

 who discovered it, was obliged, in order to succeed, to employ an extremely 

 delicate galvanometer. The direction of the electric current in the nerves is tho 

 same as in the muscles, and is therefore obtained by establishing a homogeneous 

 arc between the artificial transverse section of the nerve and its surface. A 

 current in the galvanometer is thus obtained, directed in the nerve from tho 

 section to the surface. 



In studying the electro-motor power of the nerves Du Bois Reymond has 

 made an experiment which I must by no means omit. In a fowl or rabbit he 

 takes a long nervous filament, such as a portion of the sciatic about eighty 

 millimetres long. This nerve is placed on the two cushions of the galvanometer 

 iri^such manner that a long piece of the nerve shall remain hanging down beyond 

 one or both cushions. As the two cushions of the galvanometer touch two 

 points of the surface of the nerve, there cannot be, and, in fact, there is no current. 

 This being done, let the two electrodes of any battery be applied to the part of 

 the nerve which hangs beyond the cushion, and in this part let a continuous 

 current be made to pass. There now occurs a strong deviation in the galvano- 

 meter, which indicates that a constant current is cii"culating therein, a current 

 which is directed in the interval of the nerve between the two cushions of the 

 galvanometer, like the external current of the battery. If the nerve were still 

 longer, so as to have a piece pendent beyond the other cushion, and if iu this 

 pendulous part the same current were made to pass, we should still obtain with 

 the galvanometer the current always directed in the nerve like the current of 

 the battery. Du Bois Reymond has given the name of electro-tonic to that 

 state of the nerve into which the whole nerve is thrown by a current which 

 traverses it, even in portions which are not permeated by the current. It is 

 this supposed electro-tonic state of the nerve which occasions the electric current 

 I have described, or, to speak more correctly, the electro-tonic state has been 

 imagined in order to deduce from it the existence of that current. 



I have latterly studied these phenomena with attention, and having found 

 that they are produced more readily and endure much longer in the large nerves 



