1902.] Photographic Records of the Response of Nerve, 199 



and applying them- to the diagram so as to represent by their position 

 the position of the leads. The first phase begins when the wave of 

 electrical activity reaches the first lead, and continues until it either 

 leaves the first lead or arrives at the second. The second phase begins 

 whenever the wave has both left the first lead and arrived at the 

 second. But if neither or both the leads are affected by the wave, 

 there is zero potential difference between them. 



In fig. 1 the duration of the active period is constant for all parts of 

 the conductor. This involves equality between the rate of propaga- 

 tion and the rate at which the disturbance dies out along the 

 conductor. Both the length of the wave and the duration are 

 constant. 



In fig. 2 the velocity of propagation of the development is greater 

 than that of the subsidence of the effect. Both the duration and the 

 wave-length increase regularly. The converse of this is shown in 

 fig. 3, where the wave of development travels slower than that of 

 subsidence, corresponding to a regularly diminishing wave-length and 

 also duration. 



Fig. 2. — As in Fig. 1, but the dura- Fi&. 3.— As in Fig. 2, but the duration 



tion of the active condition in- 

 creases continually, as indicated 

 by vertical lines on the left side. 

 This corresponds to an increasing 

 length, of wave, as shown by the 

 horizontal lines on the right. 



2s".B. — Time is measured verti- 

 cally downwards, and position 

 on the nerve-fibre horizontally. 



continually diminishes (left side) , 

 corresponding to a continually di- 

 minishing wave-length (right side). 



Manifestly under such conditions the response would not be propa- 

 gated beyond a limited distance. I have some reason for believing 

 that responses of this character might be obtained from kept muscle 

 with minimal stimuli. 



Up to this point there has been no marked difference between the 

 two ways of representing the problem. With fig. 4 it is otherwise. 

 Here the rate of propagation is constant, but the duration, as shown 



