CHAPTEE III 



ELECTRICAL EXCITATION OF MUSCLE 



THE electrical current undoubtedly ranks first among all the 

 artificial stimuli of irritable substances at our command. And 

 this not merely on account of its easy application, and the pos- 

 sibility of measuring its intensity by the finest gradations, but 

 above all in regard to the specific nature of its action. 



Whenever the electrical current has been referred to as an ex- 

 citation in the preceding observations, it signified almost exclusively 

 single, or rapidly repeated, induction shocks, the primary object 

 being to produce a momentary stimulus, easily varied in strength, 

 which should injure the excitable portions as little as possible. 

 But, on the other hand, the more exact investigation of the mani- 

 festations of excitation produced by the constant current in muscle 

 is of great interest, and of the highest importance in estimating 

 the mode of action of the electrical current. As regards the 

 technique of the experiments, some preliminary observations on 

 method are advisable. In all the earlier experiments on animal 

 tissues in which the electrical current served as a means of excita- 

 tion, the excitable parts were stretched over convenient metal 

 electrodes, usually made of platinum, by means of which the 

 current was led into them. The value of this method was, how- 

 ever, much diminished by the polarisation current invariably 

 associated with it, so that it became a sine qud non under all 

 conditions, to employ non-polarisable electrodes whenever constant 

 currents were made use of still more so with strong currents and 

 prolonged closure. Ever since du Bois-Eeymond enlarged the 

 technique, of electro-physiology by the invention of his unpolaris- 

 able combination of amalgamated zinc and zinc sulphate, in order 

 to lead off currents of animal electricity, these electrodes have 



