ME. W. POLE ON COLOUE-BLINDNESS. 
335 
J. Violet being to us only dark dull blue, its confusion with crimson, and that of its 
tint hlac with pink, come under the explanation above given. 
K. The remark, first made by Dalton, that crimson and pink appear to have no 
relation to the idea of red derived from vermilion or a soldier’s coat, must now be per- 
fectly intelligible. Crimson appears dark grey, pink dirty blue, but scarlet is a very 
decided yellow, and these are therefore as unrelated to each other as the yellow to grey 
of normal eyes. 
L. All scarlet hues of red are very distinctly visible as dark yellow. 
M. The hopeless perplexity into which the colour-bhnd are thrown in regard to 
green may be easily inferred from art. 15. It is to them what white or grey is to the 
normal-eyed, i. e. it represents no colour at all. The only cases therefore where it 
becomes visible as a colour, are those where it has a preponderance of yellow or blue in 
its composition. 
Q, R, W. All violets, and all greens on the blue side of the neutral, appear dark blue. 
V. If the red element in violet is much stronger than the blue, the latter may be 
overlooked, and the hue will then appear colourless or grey. 
X. This only applies to compound hues, in which the blue or yellow element (which 
alone gives the appearance of colour to our eyes) is often present in quantities so small 
as scarcely to bear toning without becoming imperceptible. With the simple colours 
blue and yellow, I believe our vision is quite as acute as that of the normal-eyed, even 
for the faintest or the darkest tones. 
21. Having now described my own case, the question arises how far this conforms 
with other instances of colour-blindness, and to what extent it may be considered as a 
type of the defect in general. 
It will be impossible for any one to examine the various cases on record without 
noticing many points of strong resemblance to the characteristics of my own vision, as 
enumerated in art. 7 ; but I am not aware that, till now, the whole of these varied and 
apparently incongruous symptoms have ever been represented as combining in one 
person. Each individual has contributed his portion to the list, by telling the story of 
his own experience ; but I scarcely suppose it has been conceived possible that any case 
should exist which would comprehend them all together, or that phenomena so difiierent 
could be brought under any simple law. Hence an opinion has prevailed that there are 
many varieties of colour-bhndness, differing much in character as well as in severity, 
each being denoted by its own peculiar symptoms, and each therefore requiring special 
classification. 
Professor Elie Waetmann of Lausanne, in a paper on Colour-Blindness, translated in 
Tayloe s Scientific Memoirs for 1846, after enumerating several different classifications 
of the disease given by different continental authorities, appears himself to be of the 
opinion that there are as many varieties of the defect as of individuals who are affected 
with it, so that, as he expresses it, no classification is possible. 
Dr. Wilson does not go to this length, but he appears to consider his cases as varying 
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