t 2j4 1 
charge in another way the fenfibility of thd 
nerves y but we are unacquainted with 
what happens in the nerves, under thefe 
different circumftances. Are the nerves 
more or lefs charged than commonly ? or 
does the re-a<5tion of the brain occur with 
too much or too little force ? Perhaps this 
laft is the moil common caufe. 
We know that the brain does not re¬ 
ceive any impreffion without re-a<5ting 
upon the nerves. All that I have faid 
upon the effedts of different ftimuli, and 
of the paffions upon the voluntary and 
fpontaneous motions, afford an incontefta- 
ble proof of this fadt. 
If this re-adlion did not happen, then 
the caufes of which we have been fpeak* 
ing, viz. the ftimuli and paffions would 
not induce any change in the animal 
economy. 
The cretins of the Vallais who are in- 
fenfible to the flimuli, which determine 
others 
