ANIMAL ELECTRICITY. LECTURE I. 11 



to current escape nor to du Bois-Reymond's electro- 

 tonic current.) 



The value at which you will be disposed to 

 estimate the electrical signs of physiological activity 

 will be greatly enhanced by the closer consideration 

 of the first experiment (on muscle). Here you have 

 in the mechanical effects of muscular contraction, an 

 obvious measure of its physiological activity — ^the 

 muscle shortens much or little according as its phy- 

 siological activity is much or little, and one naturally 

 asks himself whether with this greater or smaller 

 mechanical effect there is a greater or smaller elec- 

 trical effect. 



A very simple variation of the experiment will 

 answer us in the affirmative, and the records of 

 more prolonged observations will confirm that affirm- 

 ative beyond all doubt. 



Let us go back to the experiment on muscle, and 

 make the muscle contract much or little, watching by 

 the oralvanometer to see whether the size of the elec- 

 trical effect corresponds. It is difficult to watch two 

 things at once, so in place of the muscle itself I 

 show you the end of a lever acted upon by the 

 muscle and marking against a smoked plate that 

 runs past the lantern ; the lever is the contraction 

 indicator, and the galvanometer is the current indi- 

 cator. If now you will watch the galvanometer 

 spot while the muscle is stimulated more or less 

 strongly, you will see that the spot makes a greater 



