374 Mr Charles Bell on tJie Motio7is of the Eye. 
That gentleman has failed to observe the difference between 
vision while yet unexercised and uneducated, if one may say so, 
and after the impressions upon the eye have become, by long 
experience, the signs of the qualities and positions of bodies, the 
knowledge of which is gained through the other senses and the 
operations of the muscular frame. 
If I operate upon an infant, it may express paiuj, but it makes 
no effort to remove my hand. That motion which appears to us 
so natural, is the effect of education and experience. The candle 
before a child seems to enliven every faculty of its nature ; but 
it cannot follow that candle with its eyes when it is moved, un- 
til repeated experience has taught it to combine the action of the 
muscles with the exercise of the sense. 
If the eye of the patient, above alluded to, had been in its ori- 
ginal and unexercised condition, the vision would have been im- 
perfect in every respect, because the sign in the eye would have 
had no meaning ; but as it was, it could not be called perfect, 
since it was incapable of ranging round the outline of an image, 
or of following and corresponding with the other eye. 
We may pursue this subject a little further. When looking 
to an object in the country, we judge of its distance and place, 
by an operation as near to a trigonometrical • survey as can be. 
The eye moves from hill to tree, from the steeple to the castle ; 
and, by knowing their relative positions, we form an estimate of 
the situation and size of the object beyond them. How much 
we owe to the motions of the eye, we may know by cutting off 
the operation of the muscles, in looking through a tube. We 
then judge imperfectly of place and distance, and know no- 
thing of them but by the degree of obscurity proceeding from 
the intervening atmosphere. 
The same thing is illustrated, in looking on a panorama ; for 
there we have before us the shades and colours of natural ob- 
jects, which are their signs, but the means of comparison being 
carefully cut off, we suffer ourselves to be deluded. 
In short, it is clear to demonstration, that the eye is in conti- 
nual motion, making comparison of distances and angles, and 
thus informing us of that which we should never know, without 
the combination of the sense of vision with muscular activity. 
Even in the most minute object we examine, the eye travels over 
