ANIMAL ELECTRICITY. ^LECTURE IV. "]"] 



This is, to some extent, a preliminary dioression — 

 inasmuch as the title of these lectures is Animal Elec- 

 tricity, not Electro-physiology. Strictly speaking, the 

 former title covers only the electrical effects derived 

 froui animals, not the effects of electricit)- applied to 

 animals. But seeing that we shall very shortly have 

 to deal with polarisation phenomena which belong to 

 both categories — being electrical responses to elec- 

 trical currents; and that we shall have to examine 

 the relation between such electrical responses and 

 the ordinary mechanical responses significant of 

 physiological excitation, the digression is not merely 

 convenient and necessary, but logically defensible, 

 even if we are to be restricted to animal electricity. 

 The polar reactions of living matter are, as regards 

 their physico-chemical mechanism, of the same 

 nature as those of inert matter, but in many respects 

 the former exhibit features that are peculiar, and 

 characteristic of the living state. And while we 

 must recognise that electrolytic disruption, whether of 

 living, or of dead, or of inert matter, is of one nature 

 in its essentials, we must also recognise that, in 

 correspondence with varying conditions of greatly 

 diminished chemical stability, varying degrees of 

 greatly increased polarisability will be found in living 

 as compared with dead matter. In the course of these 

 lectures I shall show that the electrolytic polarisation 

 of living matter is extraordinarily sensitive to chemical 

 modifications that may certainly be termed slight, that, 



