Mi- Charles Bell on the Motions of the kye. SJS 
tif matter not known to us merely by the sense of touch, but 
by that sense, aided by the motions of the hand, of which mo- 
tions we are sensible ; that the entire and complete exercise of 
the sense of toucli comprehends a comparison of the exercise of 
the nerve of touch with the consciousness of, or the sensibility to, 
the muscular motion which accompanies it ; and that, without 
this combination, the sense of touch would not be entitled to the 
name of the geometrical sense. 
Following out this subject, I showed that it is possible to 
make the image of an object permanent on the retina, after the 
object itself is withdrawn from the eye ; that the image or 
phantom in the eye is stationary, whilst the eye-ball is at 
rest ; but that the slightest exertion of the voluntary muscles of 
the eye makes a change on the apparent position of that image, 
as it not Only follows the motions of the body and the headj 
if we are conscious of these motions ; but, even when the head 
is fixed, if the muscles of the eye are in action, the place of 
that image appears to be changed, whilst it is actually fixed on 
the same spot of the retina. 
A man holds a ball in his hand ; he does not see it, he only 
feels it. By what power is it, that he knows whether he hold^ 
that ball before him, or behind him Y' None of the five senses 
can aid him here : ke knows it by means of his consciousness, 
first, of the exercise of the organ of touch, —secondly, through 
the sensibility to muscular action. The action 'of the muscles 
of the arm is combined with the Sense of touch in the idea, 
formed in the mind. So, when the image is fixed upon the 
panded nerve of the eye, if the muscles strain to the right side' 
or to the left, the position of the image appears to make a cor-^ 
responding change, — because the mind is contemplating two 
operations ; the impression on the nerve, and the action of the' 
muscles. 
In the course of this investigation, I had found a case in my 
hospital, where the eye had lost the power of the muscles, with- 
out losing the power of the optic nerve ; and I had stated that 
the vision was entire, obviously meaning the possession of that 
sense which belongs to the optic nerve, in contradistinction to 
the other offices of the eye. Dr Brewster calls his reasoning oii 
this passage the reductio ad ahsurdum. 
VGL. XII. NO. APEIL 1825, B b 
