vin CONDUCTIVITY AND EXCITABILITY OF NERVE 65 



Hermann's Handbuch, ii. 1, p. 187) makes it possible that at a" 

 certain stage of localised narcosis local capacity of response 

 may have sunk considerably, while conductivity, in consequence 

 of the predominance of " longitudinal lability," is still intact 

 (Griinhagen's C0 2 experiment). Under other conditions, on the 

 contrary (as in treatment with alcohol), direct excitability declines 

 much more slowly than conductivity, as normally occurs in 

 muscle. In view of this fact, we shall hardly, with Szpilrnann 

 and Luchsinger, interpret the reaction as signifying that the exci- 

 tation, starting from a distant normal point, has to pass through a 

 longer and injured tract, losing thereby in intensity. But even 

 Gad's view of a difference in the longitudinal and transverse 

 excitability of nerve would appear to be fundamentally impossible, 

 since the inexcitability of nerve to pure transverse passage of cur- 

 rent is as well established for nerve as for muscle (Biedermann). 

 A true grasp and right interpretation of these facts will only be 

 possible when we know more about the manner in which one 

 excited section of the nerve acts as a stimulus upon that section 

 next to it. Innumerable examples show us that the excitatory 

 condition per se does not necessarily imply conduction of the im- 

 pulse to the contiguous sections. Localisation of persistent closing 

 and opening contraction, the " positive anodic polarisation " (due 

 to purely local alterations) of the narcotised muscle, the gradual 

 introduction (einschleichen) of even strong currents into nerve and 

 muscle, all prove sufficiently that the conditions of development, 

 particularly as regards time, of the excitatory process are of funda- 

 mental importance to its propagation. It is conceivable that 

 different substances might so affect the time-relations of the trans- 

 mission of excitation from section to section, that the effects in 

 question could be interpreted. 



Helmholtz, in his experiments on the motor nerves of frogs, 

 employed maximal stimuli, or else reduced the strength of stimulus 

 at one point of excitation only so far that the twitches were equal in 

 magnitude. The experiments which he undertook later with Baxt 

 (14) on man, in which the muscles of the ball of the thumb were 

 excited by stimulating the median nerve at two different places, 

 appeared to show that the latent period on exciting the distal point 

 of the nerve was regularly less with stronger excitation, while 

 at the proximal point no effect from altered strength of excita- 

 tion is perceptible. Hence we may conclude that strong excitation 



VOL. II F 



