66 ELECTRO-PHYSIOLOGY CHAP. 



is more rapidly transmitted in nerve than a weak stimulus. 

 This view finds support in the later investigations of Valentin, 

 Troitzsky, and Wundt, while Rosenthal and Lautenbach affirm 

 that conductivity is independent of strength of excitation. From 

 a recent and detailed research of v. Vintschgau (25), it appears 

 that "when a frog's nerve is initially excited at two different 

 points with that strength of stimulus (induction shocks) which 

 causes the first, or approximately the first, maximal twitch, and 

 the stimuli are subsequently increased from that point, there is a 

 certain range within which the rate of transmission of the 

 nervous excitation undergoes no essential alteration." So soon, 

 however, as this has been exceeded, the rapidity with which the 

 excitation is transmitted increases with the further augmentation 

 of the stimulus, till it becomes impossible to measure it. A. Tick 

 (26) found in the non-medullated commissural nerves of Ano- 

 donta that a strong stimulus was more rapidly transmitted in the 

 nerve-fibre than a weaker excitation, and S. Fuchs (27) has 

 recently arrived at the same result in determining the rate at 

 which the negative variation is transmitted in the nou-medullated 

 nerves of the mantle of Elcdone. 



II. PHENOMENA IN FIBRES ASSOCIATED WITH NERVE-CELLS 



(IiKFLEX ACTIVITY) 



At this point it is desirable to discuss the question whether 

 the interpolation of ganglionic elements upon the course of the nerve- 

 fibre has any, and if any, how much, effect upon the transmission of 

 excitation. 



In stimulating motor fibres outside the central organ, this 

 question has of course but little application ; the most that can 

 be ascertained is whether the transmission of excitation from nerve 

 to muscle produces any perceptible delay in conduction or no. 

 Certain experiments of Bernstein (infra} seem to indicate that 

 such is the case. 



Far greater importance attaches to the interpolation of 

 ganglion -cells, in all excitatory experiments where parts of a 

 central organ are excited directly, or by means of centripetal 

 nerves. Exner (28) examined into the seemingly simple case 

 in which the only question is whether the interpolation of a 

 single ganglion -cell effects any marked alteration in rate of 



