12 ANIMAL ELECTRICITY. LECTURE I. 



or smaller movement, and turning to the muscle 

 you will see that the muscle has contracted more 

 or less strongly. 



This is a very simple but very important fact, 

 as a link in the argument that electrical changes 

 are a measure of physiological activity. More and 

 less muscular action involve more and less chemical 

 change, a larger and smaller diminution of the 

 current of injury. And whereas by arousing the 

 quiescent muscle you get a negative variation of 

 the current of injury, you would get a positive varia- 

 tion of the same by "quelling" an active muscle. 

 To be fully assured of this correspondence between 

 the mechanical and electrical effects of this one 

 cause — chemical activity, pray look at this double 

 record, where the white line gives series of contrac- 

 tions and the black line the corresponding series 

 of electrical effects of one and the same muscle 

 (fig. 6). 



Each of the two series exhibits a declining effect — 

 the expression of muscular fatigue — and the rate of 

 decline is nearly the same in both cases. Not quite 

 the same, however ; if you examine the twin record 

 at all critically, there are evident divergences ; the 

 two records do not tell precisely the same story ; and 

 although the point is not one upon which we need 

 dwell now, I may observe that of the two versions — 

 the mechanical and the galvanometric — the latter is 

 the more accurate. It gives a declining series of 



