14 THE SIGNS OF LIFE [LECT. 



through it from B to A (while when it was excited near A there 

 was current in it from A to B). 



Is there any doubt in your mind whether these have been 

 physiological responses, for which the essential condition is that 

 the ivy petiole should be alive ? There should be such a doubt 

 in your mind, and you should set the doubt at rest by repeating, 

 or making me repeat, the experiment on a petiole of which the 

 molecular mobility has been abolished, i.e., on a petiole that has 

 been killed or otherwise immobilised. I might kill it at once by 

 plunging it into hot water, but to do this I should have to 

 remove it from the electrodes and replace it, which takes time ; 

 and even at best, when the petiole has been replaced as carefully 

 as possible as it was, you cannot be quite sure that I have 

 exactly replaced the petiole. So I shall otherwise immobilise 

 it, in a way that will allow me to leave petiole and electrodes in 

 statu quo, viz., by sending through it currents of such strength 

 that the living stuff will be completely stunned : which I now 

 do, and then repeat both trials as before, exciting at A and then 

 at B, without, as you see, any response in either case. The 

 previous effects you witnessed were therefore physiological. 



8. " Zincative." So far so good, there is no doubt what- 



O ^ 



ever about the facts, the excitatory currents are precisely such 

 as are aroused by excitation of animal protoplasm. But how 

 are we to label them ? 



Following the best authorities Faraday, Maxwell, du Bois- 

 Reymond we should say, referring to the pole under our 

 observation, that B, the excited spot, is negative to A, the non- 

 excited spot (or A, the excited spot, negative to B, the non- 

 excited spot ; but since this confirmatory experiment is confusing 

 we will henceforth omit it, and consider only B excited, and A 

 non-excited). 



And as a matter of fact, this has been the terminology 

 followed by physiological writers. 



But in course of time, and especially in consequence of the 

 polemic that took place between du Bois-Reymond and 

 Hermann, the meaning of the term " negative " underwent a 

 curious twist. Du Bois-Reymond found that the " resting 



