SENSE OF VISION PERCEPTION OF SOLIDITY. 761 



tactile ; and yet it constantly occurs to us, on looking on a surface which re- 

 flects light in a particular manner. But if it were not for the association 

 which experience leads us to form, of the connection between polish as seen 

 by the eye, and smoothness as felt by the touch, we should not be able to de- 

 termine, as we now can do, the existence of both these qualities, from an 

 impression communicated to us through either seuse singly. The general 

 fact that, in Man, the greater part of those notions of the external world, 

 by which his actions in the adult state are guided, are acquired by the 

 gradual association of the two sets of perceptions derived through the Sight 

 and through the Touch, is substantiated by amply sufficient evidence; this 

 being chiefly derived from observations made upon persons born blind, to 

 whom sight has been communicated by au operation, at a period of life 

 which enabled them to give au accurate description of their sensatious. The 

 case recorded by Cheselden is one of the most interesting of these. The 

 youth (about twelve years of age), for some time after tolerably-distinct 

 vision had been obtained, saw everything flat as in a picture, simply receiv- 

 ing the consciousness of the impression made upon his retina ; and it was 

 some time before he acquired the power of judging, by his sight, of the real 

 forms and distances of the objects around him. An amusing anecdote re- 

 corded of him, shows the complete want which there is in Man, of any natu- 

 ral or intuitive connection between the ideas formed through visual andi 

 through tactile sensations. He was well acquainted with a Dog and a Cat 

 by feeling, but could not remember their respective characters when he saw 

 them ; and one day, when thus puzzled, he took up the Cat in his arms, and 

 felt her attentively, so as to associate the two sets of ideas, and then setting 

 her down, said, " So, puss, I shall know you another time."- A similar in- 

 stance has come under the Author's own knowledge ; but the subject of it 

 was scarcely old enough to present phenomena so striking. One curious cir- 

 cumstance w'as remarked of him, which fully confirms (if confirmation were 

 wanting) the view here given. For some time after his sight was tolerably 

 clear, the lad preferred finding his way through his father's house (to which, 

 he had been quite accustomed when blind) by touch rather than by sight,, 

 the use of the latter sense appearing to perplex instead of assisting him ; but,, 

 when learning a new locality, he employed his sight, and evidently per- 

 ceived the increase of facility which he derived from it. 1 The actions per- 

 formed by many newborn animals do not constitute any valid objection to 

 the view that such visual perceptions are for the most part acquired by Man ;. 

 for all that is indicated by them is, that certain sensations give rise to move- 

 ments adapted to supply the wants to which they relate; and they do not 

 afford any proof that definite notions, such as we entertain, of the forms and 

 properties of external objects, are possessed by the animals which exhibit 

 them. We shall now examine, a little more in detail, into the means by 

 which we gain such notions, and the data on which they are founded. 



620. The first point to be determined, is one which has been a fruitful 

 source of discussion, the cause of erect vision, the picture upon the retina 

 being inverted ; and with this is connected the general question of the origin 

 of our Sense of Direction. The difficulty which has been raised in regard to 

 the former subject, is rather apparent than real ; being founded on .an errone- 

 ous notion of the nature of the Visual sense. For it seems to have been 

 supposed that we look at the retinal picture with the "mind's eye," just as 



1 The question has been proposed, whether a person born blind, who was able by 

 the sense of Touch to distinguish a cube from a sphere, would, on suddenly obtain- 

 ing his Sight, be able to di?tinguish them by the latter sense. This question was 

 answered by Locke in the negative ; and, as appears from the facts above stated, with 

 justice. 



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