162 PROFESSOR WARTMANN ON DALTONISM, 
ple and few as palliatives of their imperfection ; unhappily such 
an undertaking does not seem possible, and we may say that 
there are as many varieties of daltonism as of individuals who 
are affected with it. 
I prefer, in consequence, to throw aside every systematic no- 
tion which may not have in its favour a sufficient proof, and only 
to separate the cases of dichromatic daltonism and of polychro- 
matic daltonism, that is to say, where there are more than two 
colours perceived normally. With regard to the very rational 
distinction which M. Seebeck has the merit of having first esta- 
blished between the errors of appreciation of intensity, and those 
of judgment of the individual kind of colours, it is to be regretted 
that we cannot make it in the great majority of the descriptions 
which writers have transmitted to us. We must content our- 
selves with recommending it to those physiologists who may be 
engaged upon this complex subject. 
I add, lastly, in favour of my opinion, that there exist a great 
number of different degrees in daltonism. When there are only 
two colours perceived, they commonly are reduced to a vague 
sensation of light and darkness: the influence of the red rays is 
almost null. But from this point to the case in which there are 
only errors in the appreciation of tints equal in brightness and 
approaching in colours—errors which only occur in artificial 
light, and which constitute the extreme limit of daltonism,—the 
number of intermediate degrees is undetermined and perhaps 
unlimited*. 
§ 2. Cases of Dichromatic Daltonism. 
The most ancient of those which have been described was © 
related by Dr. Dawbeney Tubervile+ in 1684. He says that a 
* It is this great number of varieties of daltonism which appears to me an 
objection against the proof which Sir David Brewster has thought he found 
in this anomaly in support of his theory of three elementary colours (Edinb. 
Journ. of Science, N.S., vol. v. p. 19. Bib. Univ. tome |. p. 147). It cannot 
be said that “the physiological fact and the principle of optics on which he ~ 
founds his analysis of the spectrum are perfectly in accordance and confirm 
one another.”” [On this Sir David Brewster remarks (Phil. Mag. Aug. 1844, 
p. 138), “* What Prof. Wartmann calls my theory of three elementary colours 
is a fact as rigorously demonstrated as any physical truth can be; but if he 
does not admit it as ¢rue over the whole length of the spectrum, he cannot 
avoid, if he makes the experiments, admitting it as true over the greater part 
of it; and this is all that is necessary for my present argument,”—Ep. 
+ Two letters from the great and experienced oculist Dr. Dawbeney Tuber- 
vile of Salisbury, to Mr. William Musgrave of Oxon, containing several re- 
markable cases in physic relating chiefly to the eyes.—Phil. Trans. No. 164, 
p- 736 (Aug. 4, 1684). Lowthorp’s Abridgement, vol. iii. part 1. p. 40. 
