[ 205 ] 
undoubted. It is equally certain that its 
commands are lucceeded by a change in 
the origin of the nerves, that this change 
is extended along their courfe, and that 
the parts upon which they are diftributed, 
are perceptible of its influence in a degree 
proportioned to the firfl: impulfion. 
The origin of a nerve is a fmall or¬ 
gan of a very particular defign. It 
is here that the mind holds its empire, 
though it is impoffible to demonftrate how 
this is effedled, and beyond this point its 
power ceafes. A proof of this affertioii 
is evident, in my opinion, from the fol¬ 
lowing obfervation:—Suppofe a frog to 
be divided into two portions by being cut 
acrofs the body, its poflerior extremities, 
the nerves of which are fent from the me¬ 
dulla fpinalis, move about in the fame 
way as if they were dill attached to the 
body of the living animal. The move¬ 
ments become ftronger when preffure is 
/ , 
applied. 
f 
