44 Prof. J, 



Burdon-Sanderson. Relation of Motion in Animals 



•ence of potential comes into existence abruptly, and subsides abruptly 

 at first, afterwards less rapidly. (P in Diagram 4.) 



Xow I have found that in the study of my experimental results it 

 is of great advantage to proceed a priori. Let us assume that there 

 are three types of stimulation, and that each has its form of response. 

 We can best begin by inquiring to which of these three forms the 

 •observed variation belongs, and then determine in what respects it 

 conforms with, or differs from, the type. 



In the diagrams, I have shown the types of photographic curves 

 which correspond to the three forms of response to stimulation I have 

 indicated. The faint lines represent photographic curves ; the strong, 

 variations of potential-difference. In each diagram the strong and the 

 faint lines have been drawn in their true mathematical relation to each 

 other, i.e., so that the vertical distance apart of strong from faint is every- 

 where proportional to the gradient or slope of the photographic curve, the 

 proportion being such that if the E.M.F. of the current acting on the electro- 



