BLIGHT. See AGRICULTURE Index.
an epithet applied to a living creature en tirely deprived of the sense of sight. It belongs to medicine to point out the method of curing or alle viating- this malady, in cases Avhere it admits of cure or palliation. What we propose in this article, is, to examine the mental, rather than the bodily state of those individuals of the human species, who have been destitute of eye-sight from earliest infancy ; to estimate the privations under which they labour, and the expedients by which these may be most suc cessfully compensated ; to inquire into their capacity of enjoyment, and of mental improvement ; and the proper means of rendering them comfortable in them selves, and useful members of society.
r It was put as a question, by Mr Molineux to Mr Locke, whether a person, blind from his birth, would, upon being suddenly restored to sight, be able to distinguish, by his eyes alone, a globe from a cube, the difference of which he was previously aware of by feeling ? Both these gentlemen were of opinion, that the distinction could not be made by such a person by the sight till first assisted by the touch; and their conclusion seemed amply confirmed by the experience of several persons, who, having been afflicted with cataracts from their earliest years, and afterwards receiving their sight by the opera tion of couching, appeared at first unable to distin guish any one thing from another, however different in shape and magnitude. A very remarkable case of this kind has been detailed by Mr Cheselden, the ce lebrated anatomist, in No. 402. of the Philosophical Transactions, of a young gentleman, who was couched by him in the 13th year of his age. As it tends greatly to illustrate our present subject, as well as the general nature of vision, we shall insert its _most interesting particulars, in Mr Cheselden's own words.
f 4 Though we say of this gentleman, that he was blind, as we do of all people who have ripe - racts, yet they are never so blind from that cause, but that they can discern day from night ; and, for the most part, in a strong light, distinguish black, white, and scarlet : but they cannot perceive the shape of any thing. For the light by which these perceptions are made, being let in obliquely through the aqueous humour, or the anterior surface of the crystalline, (by which the rays cannot be brought to a focus upon the retina,) they can discern in no other manner, than a sound eye can through a glass of broken jelly, where a great variety of surfaces so differently refract the light, that the several distinct pencils of rays cannot be collected by the eye into ;their proper foci ; wherefore, the shape of an object in such a case, cannot be at all discerned, though the colour may : And thus it was with this young gentleman, who, though he knew these colours asunder in a good light, yet, when he saw them ter he was couched, the faint ideas he had of them before, were not sufficient for him to know them by afterwards ; and, therefore, he did not think them 7 the same which he had before known by those names.
Now scarlet he thought the most beautiful of all co lours,. and of others the most gay were the most pleasing ; whereas the first time he saw black it gave him great uneasiness, yet after a little time he was reconciled to it ; yet some months after, seeing, by accident, a negro woman, he was struck with great. horror at the sight.
" When he first saw, he was so far from making any judgment about distances, that he thought all .objects whatever touched his eyes, (as he expressed it,) as what he felt did his skin ; and thought no ob jects so agreeable as those which were smooth and regular, though he could form no judgment of their shape, or guess what it was in any object that was pleasing to him. He knew not the shape of any thing ; nor any one thing from another, however different in shape or magnitude ; but, upon being told what things were, whose form he before knew from feeling, he would carefully observe, that he might know them again ; but having too many ob jects to learn at once, he forgot many of them, and (as he said) at first he learned to know, and. again forgot, a thousand things in a day. One particular only, though it may appear trifling, I will relate. Having often forgot which was the cat and which the dog, he was ashamed to ask ; but catching the cat, (which he knew by feeling,) he was observed to look at her stedfastly, and then, setting her down, said, So, puss, I shall know you another time.