252 ON ACCIDENTAL OR SUBJECTIVE COLORS. 



false; o-^cg, sight— =■ the phenomena which, with M. Wartmann, we have desig- 

 nated by the more simple term Daltonism. He distinguishes five classes of 

 daltonians : 1st. That of persons in whom the sense of color fails almost com- 

 pletely, and who see in place of the principal colors, yellow, red, and blue, only 

 different degrees of white and black. The existence of this class is doubtful, for 

 all eyes have at least the sensation of yellow. 2d, That of persons who distin- 

 guish the yellow. To these external objects appear colored with the tints pro- 

 duced by different combinations of yellow, blue, and black. 3d. That of per- 

 sons who not only see yellow, but are moreover cajjable of a peculiar and uni- 

 form perception of blue and red ; these are the akyanopists of Goethe. 4th. 

 That of persons only destitute of the perception of red, which appears to them 

 ashy-gray. 5th. That of individuals who distinguish all the colors, but not in 

 a distinct manner : instead of being able to discriminate the mixture of two 

 colors, they see but one of them. These divisions are rather arbitrary than 

 real ; they seem to us suggested by an incomplete and hypothetical study of 

 the facts. We should have much confidence in M. Szokalski as a practical 

 oculist, but his pamphlet proves that he is not a competent physicist ; it might 

 be said, indeed, that he has undertaken to wrest daltonism completely from the 

 domain of physics. "The immediate cause," he says, "of chromato-pseudopsy 

 consists in the confusion of the determinative functions of the brain which fur- 

 nish us with the perception of colors." This is evidently an error ; before the 

 confusion of the functions of the brain — an imaginary confusion probably — there 

 is certainly a physical cause, the insensibility of the retina. M. Szokalski is 

 convinced that the physicists have but false ideas of colors : while they are en- 

 tirely and essentially subjective, the physicists have made them objective by 

 forgetting the important part which our eye plays in their production. We 

 shall not stop to repel a reproach which has no foundation ; there is no physi- 

 cist who does not admit that colors are produced in our eyes; that the sensation 

 of color depends on a certain change in the eye, a change which is caused by 

 the operation of some stimulus. Yet more than this : the different sensations of 

 red, orange, &c., arise necessarily from different stimulants ; in each luminous 

 ray, therefore, there is evidently a distinctive character which fits it for deter- 

 mining such or such a sensation, and it would seem then quite natural to at- 

 tribute to it the color. But we leave these useless discussions and proceed to 

 analyze the much more methodical memoir of M. Elie Wartmann. 



Numher of Daltonians. — The number is much more considerable than is 

 commonly supposed. M. Seebeck detected five daltonians in rather more than 

 forty youths who composed the two higher classes of a gymnasium in Berlin, 

 and Professor Pierre Prevost has asserted that among twenty individuals there 

 is at least one who is a daltonian. 



Characteristic signs. — Are there any means of deciding, from simple inspec- 

 tion of the eye, whether daltonism exists? M. Wartmann hesitates to affirm 

 that in all cases the reply should be negative. It would seem that the daltonians 

 whose eyes are of a hazel brown sometimes offer, under an incidence more or 

 less oblique, a yellow reflection of a peculiar tint, the presence of which may 

 lead us to suspect daltonism. It has been erroneously assumed that there were 

 more daltonians with blue than with black eyes. 



Apportionment as to sex. — It can scarcely be doubted that daltonism is much 

 more common in men than women. M. Szokalski having assembled a number 

 of women and showed them separately specimens of variously colored riband, 

 requested each of them to indicate the name and nature of the colors. He was 

 struck with the perfect accord which existed among all their answers. The 

 same trial, made with a certain number of men, was far from yielding the same 

 result. Scarcely were the same specimens shown to them, when a lively dis- 

 cussion arose among them on the names of the colors. The faculty of discern- 



