v.] MUCOUS MEMBRANES 87 



by + and break induction shocks. You see that to both 

 directions of excitation the response has been a deflection 

 to your right, signifying current of positive or outgoing direc- 

 tion. 



54. Mucous membranes. These two experiments are in 

 accord with our theoretical forecast, but that they prove that 

 forecast to be a .true guess, or even bear it out to any serious 

 extent, I shall be the last to urge. The two facts (both of 

 which are representative results based upon a sufficient number 

 of trials) are, however, interesting in themselves, whether this 

 or any other explanation be the true one. With regard to the 

 digestive mucosa, I prefer, for lack of sufficient experience, not 

 to show you any experiment at all, for I am at present by no 

 means sure what is to be considered as a typical and what as 

 an exceptional result. I have seen ingoing response * more 

 frequently than outgoing response, but I desire to study the 

 conditions and magnitude of the response before coming to 

 any conclusion as to which is the typical one.* 



I would rather show you another pair of experiments, 

 illustrating in a different way the apparent opposition of 

 direction in the blaze-currents of vegetable and of animal 

 " skins." 



55. Intact surfaces. --We want to test, e.g., the skin of 

 an animal, or of a vegetable, without previous injury of the 

 surface. A very little reflection will convince us that this can 

 only be done by applying what has already been alluded to 

 above as the ABC method, viz., stimulating through A B, and 

 leading off through either A or B and a third indifferent 

 point C (p. 69). 



The three electrodes, ABC, are applied to three separate 

 external spots of a piece of frog's skin. I intend to test the 



* From further observations made subsequently to the delivery of these 

 lectures, I think the above statements may be considerably hardened. 

 In the great majority of cases so great that we may reckon an opposite 

 result as exceptional the mucosas manifest ingoing response to both 

 directions of excitation. 



