14 ANIMAL ELFXTRICITY. LECTURE I. 



which the tops He In a curve convex towards the base 

 line ; and if I had adopted a rather better mechanical 

 method (the so-called "isometric" method by which 

 the muscle is made to record its tension against that 

 of a stiff spring which allows the muscle to shorten 

 but very little) you would have witnessed a declining 

 series of tension effects much more like the gal- 

 vanometer series. But we shall come back to this 

 point in dealing with the subject of fatigue ; for the 

 present I am only concerned to establish in your 

 opinion that the galvanometer is a good indicator of 

 physiological modifications ; later I shall hope to 

 convince you that it is in this respect the best 

 and most accurate indicator at our disposal. 



To watch the alterations of physiological activity 

 taking place in fatigue or under other influences it 

 matters little as regards the muscle itself whether 

 you make use of a lever or of a galvanometer as 

 your indicator. Each record is almost a replica of 

 the other, and contrary to your expectation perhaps, 

 the less obvious method by galvanometer, once the 

 preliminary difficulties have been overcome, is easier 

 to work, as well as far more delicate and more 

 accurate than the mechanical method. 



More than one very significant inference arises 

 from this simple observation, but 1 shall only com- 

 ment upon one at this stage — to wit that the 

 electrical effect is an exact measure of action in 

 muscle, and may therefore be appealed to as a 

 measure of action in nerve. 



