338 
ME. W. POLE OX C0L0L’E-BLI^’D2s'ESS. 
a fourth black, a fifth orange, a sixth violet ; — fi’om which the normal-eyed examiner, 
impressed with the unity of greenness, may naturally infer that each person is suflfeiing 
under a ditferent species of the disorder ; while by proper interpretation these anomalous 
descriptions would only convey the expression of one consistent truth, and one perfectly 
uniform defect of vision. 
25. Guided by these considerations, as arising out of my o'v\ti experience, I have care- 
fully examined all the published cases accessible to me, and I generally find that I can 
understand and enter fully into the feelings of the witnesses ; can put myself in their 
places, and see, as it were, with their eyes ; and, recollecting what my ideas of my own 
sensations once were, I feel I can adopt by far the greater part of the testimony as 
my own. The explanation of my case comprehends and accounts for, with trifling 
exceptions, the whole varied range of symptoms described by others ; and I think there 
are fair grounds for believing that the few discrepancies that exist are but apparent, 
and admit of being satisfactorily explained away, on the grounds above alluded to. It 
appears to me, therefore, a reasonable inference, that the great majority of cases of 
colour-blindness hitherto described, correspond in general nature with my own. 
26. And I think there must be great difficulty in finding any hypothesis, except that 
of perfect dichromic vision, which will satisfactorily account for the facts observed. 
Take for instance the most common symptom, the confounding of red and green. If it 
be assumed that either of the colours presents its proper sensation to the coloirr--bhnd. it 
is difficult to avoid the inference that this colour ought always to be recognized ; but 
this is not so, red and green being generally both mistaken. 
It has been sometimes thought that red may be visible only in a partial degree ; but I 
can scarcely conceive what a partial vision of red can mean, or what mistakes of coloru- 
it ought to give rise to ; for it would be only a perversion of language to say that red is 
partially visible when it appears yellow, green, or grey. If red is really the most positive 
and individual of all colours, as it is usually described, one would think that any percep- 
tion of its true sensation should lead to a much more perfect and consistent identifica- 
tion of it than is generally found in the colour-blind. I am not only sui-e of my o\^-n 
insensibility to red, but I cannot see, in the testimony of other colour-blind persons, any 
satisfactory evidence that the true sensation of the noloui- is really perceptible to them. 
It has also been imagined that though full colours may be properly discriminated, 
they may lose their individuality in their light or dark tones ; but I cannot see any 
proof of this supposition, or that, if admitted, it would aflbrd any sufficient explanation 
of the phenomena. 
It would be desirable to direct further inquhies to this part of the subject, in order 
to discover whether the apparent varieties in the cases are merely due to the nature of 
the testimony, or whether they really indicate true variations in the character of the 
vision. If the latter, it would surely not be difficult to reduce them to some kind of 
consistent classification, and to determine, with more precision than hitherto, what are 
the real chromatic perceptions causing the diflerent classes of symptoms observed. 
