1902.] Photographic Records of the Response of Nerve. 



205 



A. The points of origin of the wave of activity in the several linear 



conductors may be differently situated in the bundle. 



B. The development of the E.M.F. at any given point of a linear 



conductor may be gradual, and so also may its subsidence., 

 and the rate of subsidence may be different from the rate of 

 development. 



C. The constituent linear conductors may not all extend to both of 



the leads selected. 



A. Influence of the Position of the Points of Origin in a Bundle of Linear 



Conductors. 



Let the points of origin jp l5 P 2 , P 3 , . . . . V n referred to O as origin 

 of co-ordinates, be pi, p 2 , Pb, .... p n - 



A B p D 



Fig. 9. — A bundle of linear conductors, connected with the electrometer at any 

 two of the points A, B, D. P x . . . . P w are the points at which the electro- 

 motive change originates. 



(1.) It is evident that with respect to the leads A andB, the duration 

 of each phase of the effect will be alike for all the linear conductors,, 

 namely, (b - a) /v. 



But the initial delay will differ for each, being (p 1 - b)/v, (p>2 - b)jv, 

 &c, the amount of this difference being (p 2 -pi)/v, &c. 



If all the conductors constituting the bundle were perfectly insulated 

 from each other, since all the E.M.F.'s would be in parallel, there 

 would be no higher P.D. produced by the joint action of any number 

 of conductors. But if, as is probable, the short-circuiting is con- 

 siderable, though of undeterminable amount, it may be assumed pro- 

 visionally that the effective P.D. between the leads varies directly 

 according to some function of the number of active conductors in the 

 bundle. The problem then resolves itself into one of summation. 



The " duration " of the effect, so far as the wave-front is concerned, 

 is counted from the beginning of the earliest to the end of the latest 

 effect. Hence the duration must be dependent partly on the dis- 

 tribution of the points of origin in the several linear conductors con- 

 stituting the bundle. 



Each conductor, as it flashes into activity, keeps up the P.D. for a 

 time given by t = (b — a)/v, but its contribution arrives early or late 

 according to the position of P. 



We may therefore write, 



h = (2h-b)/v; t a = (p tl -a)lv, 



