1910.] The Effect of some Local Anesthetics on Nerve. 431 
maximal response. From this and other data Gotch urges that submaximal 
response in muscle, and in nerve, invariably implies maximal response of a 
limited number of fibres, rather than submaximal response of the whole (or 
of any) of them; in other words, that the response of individual fibres in 
both cases is, as in the heart, “all or nothing.” In the case of muscle, this 
contention is endorsed by Keith Lucas* (v. infra). In the case of nerve, 
as judged by muscle, our observations appear to lend some support to 
the view. 
The relation of the anesthetic block to the intensity of the stimulus has 
already been mentioned (v. supra, p. 433). 
A block to response, evoked by a maximal stimulus, is complete for 
stimuli which (on the Berne scale) are several hundred times as intense, 
and this block only fails when the secondary coil is pushed up to the region 
where, in the absence of block, single induction shocks evoke the super- 
maximal twitches described by Fick. 
It is doubtful that induction shocks of this intensity are in reality single 
stimuli. Whether so or not, they are noticeably injurious to the nerve 
(cf. Locket), so far reducing its excitability that a normally maximal stimulus 
may for some minutes produce no response, and when at all, not then 
response of the original amplitude. Their effect cannot therefore be regarded 
-as normal physiological excitation. 
Considering, therefore, the failure of the local anesthetics to reduce the 
amplitude of the nerve impulse without extinguishing the muscular response 
altogether, in conjunction with the markedly restricted (if existent) ability 
-of increased (single) stimuli to evoke response through any anesthetic block, 
it seems legitimate to conclude in agreement with Gotch that, apart from 
summation, the range of amplitude in the normal nerve impulse is exceed- 
‘ingly small—in short, that the response of individual fibres is substantially 
‘maximal or zero. 
The records of recovery, when the drug solution is replaced by normal 
‘Saline, are, mutatis mutandis, similar to those of failure of response. 
The muscle twitch either returns early and grows rapidly and abruptly 
(after a weak anesthetic bath), or later and by a more or less protracted 
series of abrupt steps (after a strong aneesthetic bath), as seen in fig. 1. 
Records similar to the latter are described by Keith Lucas* as resulting 
from indirect stimulation of muscle, by single induction shocks, when these 
are gradually increased from subminimal to maximal. This step-growth in 
* Keith Lucas, ‘J. Physiol., Cambridge,’ 1905—6, vol. 33, p. 125, and 1909, vol. 38, 
‘p. 125. 
t F. S. Locke, zbzd., 1900—1901, vol. 26, p. xxxix (‘ Physiol. Soc. Proc.’). 
2. Kez 
