Fia. 5 (Exps. 750 B and 751). — Besponse of Non-medullated Nerve (upper) and 

 Medullated (lower) to Single Shocks. Same nerves as figs. 3 and 4. 



ulnar of cat). The full analysis of these will be considered in a subse- 

 quent paper, but these figures show {inter alia) that the electrical! 

 resistance plays an unimportant part in the production of the 

 phenomena observed, and that the rate of transmission of the electrical 

 effect is very much less in the non-medullated nerves. 



As, therefore, the progressive diminution in the negative variation is 

 characteristic of non-medullated nerve, both here and in cold-blooded 

 animals,* further experiments were undertaken to ascertain whether 

 this was due to events occurring along the whole length of the nerve,, 

 or to changes localised at the place of excitation. Two pairs of 

 platinum wire electrodes were used for stimulation, placed respectively 

 further and nearer the leading-off electrodes; the nerve was excited 

 first at the " far " pair and then at the " near." 



In Experiment 718 (fig. 6) the result of exciting through the near 

 pair of electrodes was to increase the negative variation to very nearly 

 the original amount (a). After 12 minutes of excitation at this point 

 the current was again sent through the "far" electrodes, and the 

 resultive negative variation (c) was much less than the original value. 

 If the nerve had been simply resting, instead of being excited at a 

 proximal place, the negative variation would have been increased 

 (see fig. 1) ; the effect, therefore, of passing a recently excited spot is- 

 diminution. 



In Experiment 719 the excitation was through three pairs of 



* Sowton, loc. cit. 



