112 



THE SIGNS OF LIFE 



[LECT. 



probably think, as I do, that an organ with two effective 

 epithelial layers, even if one of these layers is greatly more 

 effective than the other, is not the most suitable object to 

 afford contrary electrical effects significant of contrary chemical 

 changes. It would have been preferable if Biedermann had 

 based his case upon contrary electrical effects of a single 

 mucous surface. And I think that when you have reflected 

 upon the conditions of the problem, you will realise as a 

 clear economy of labour and an escape from much perplexity, 

 to methodically follow the ABC plan for the separate examina- 

 tion of the single points A and B of a simple mucous surface. 

 I have done so to some extent, but by no means sufficiently. 

 As far as I have gone, I find that the electrical response of a 

 mucous surface may be ingoing or outgoing, but that it is 

 usually the former. Here, e.g., is the record of a series of 

 ingoing responses of a frog's stomach : 



a L IOOCQ br. 



Serosa. 



FlG. 47. Frog. Stomach. Two series of ingoing responses to ingoing single 

 break induction shocks at one minute intervals. Interval of one hour between the 

 first and second series. 



| 69. A warning. Let me here put you on your guard 

 against a fallacy to which I was myself hardly alive in the 

 first comparisons of anode versus kathode, and surface against 

 surface. It is important that the area of contact between 

 surface and electrode shall, as far as possible, be equal on 

 both sides and not accidentally extended by excess of clay or 

 by fluid used to moisten the electrodes. As a matter of fact, it 



