324 
ME. W. POLE ON COLOUE-BLINDNESS. 
hundred. Of these again but a small proportion know of their defect ; still fewer have 
caied to examine themselves upon it; and there are only a much smaller minority still, 
who, being accessible, have qualified themselves to explain their "^iews in such a manner 
as to represent them faithfully . For it is important to consider that it is by no means an 
easy thing for a colour-blind person to explain his impressions to a normal-eved one in 
language free from misapprehension ; and I shall hereafter have occasion to show that for 
this reason eironeous inferences may often be drawn from perfectly honest testimony. 
But let him be the inquirer instead of the witness, and the case is wholly reversed ; 
he may collect evidence about colours in every possible shape, from the scientific investi- 
gations of the philosopher to the artless remarks of the child ; he need not go far for an 
answer to any question he may choose to put, however abstruse ; and as to common facts, 
almost every one he meets is a competent witness from whom he may gather them. 
I conceive, therefore, that the careful and patient investigation by any colour-blind 
person of his own case, supposing him to embrace the opportunities open to him for 
ascertaining clearly and fully the ordinary facts and impressions regarding colour in 
general, is likely to lead to a more faithful representation of the phenomena, than when, 
as is usually the case, the comparison is undertaken by the normal-eyed. 
3. It is not necessary for me to enter into the optical theory of colour’s generally. I 
only require the means of illustrating, in the simplest manner possible, the facts I have 
to bring forward ; and this, I conceive, may be sufiiciently done by reference to well- 
known colours in ordinary use. And as it is convenient to adhere to some definite 
system of colour-nomenclature, I propose to adopt, for the pur-poses of the paper, the 
popular hypothesis that there are three primary colours, red, blue, and yellow, by 
combinations of which all hues in nature may be supposed to be formed. 
4. The existence of a defect in the eye, which gives rise to an abnorrrral rision of 
colours, is now well established. Its nature has been discirssed, aird descriptions of cases 
have been published, within the last few years, by various writers ; birt it will be suffi- 
cient here to refer to the latest and most complete work on the subject, rramely, that bv 
Professor Wilson of Edinburgh*, who has made this defect his particular study. 
5. Dr. Wilson considers colour-blindness, existing in eyes otherufise normal, as of 
three kinds : — 
A. Inability to discern any colour, properly so called ; so that black and white, ?. e. 
light and shade, are the only variations of tint perceived. Cases of this total blindness 
to colour are very rare. 
B. Inability to discriminate the nicer shades (hues) of the more composite colours. 
This is so frequent as to be apparently rather the rule than the exception ; and more 
than one of our most eminent artists have expressed to me their comiction that there 
are very few people who have a perfect appreciation of the nicer distinctions of colour. 
It is, however, probable that this often arises rather Aom want of education of the eye, 
or want of ability to describe the impressions perceived, or both combined, than from 
* Eesearches on Colour-Blindness. By Geoege Wilsox, M,D., E.E.S.E. &c. Edinburgh, 1855. 
