98 AN INQUIRY INTO THE FUNCTIONS OF THE VISCERAL NERVES 
result of nervous exhaustion continued during so long a period, such speedy 
recovery could hardly, one would think, have taken place. 
These and other considerations, to which the already excessive length of 
this letter forbids me to allude, induce me to think it safest in the present state 
of science to regard as a fundamental truth not yet explained, that one and 
the same afferent nerve may, according as it is operating mildly or energetically, 
either exalt or depress the functions of the nervous centre on which it acts. 
It is, I believe, upon this that all inhibitory influence depends, and I suspect 
that the principle will be found to admit of a very general application in 
physiology. 
1 amnecc: 
JosEPH LISTER. . 
