COLOR-VISION AND COLOR-BLINDNESS. 697 



regard to the color of the signals which had beeu displayed. Professor 

 Holmgren, of the University of Upsala, had his attention called to 

 this discrei^ancy, and he fonud, on further examination, that the wit- 

 ness whose assertions about the signals differed from those of other 

 people was actually color blind. From this incident arose Professor 

 Holmgren's great interest in the subject, and he did not rest until he 

 had obtained the enactment of n law under which no one can be taken 

 into the employment of a Swedish railway until his color-vision has 

 been tested, and has been found to be sufficient for the duties he 

 will be called upon to perform. The example thus set by Sweden has 

 been followed, more or less, by other countries, and especially, thanks 

 to the untiring labors of Dr. Joy Jeffries, of Boston, by several of the 

 United States ; while at the same time much evidence has been col- 

 lected to show the connection between railway and marine accidents 

 and the defect. 



It has been found, by very extensive and carefully conducted exam- 

 inations of large bodies of men, soldiers, policemen, the workers in great 

 industrial establishments, and so forth, as well as of children in many 

 schools, that color-blindness exists in a noticeable degree, as I have 

 already said, in about 4 per cent, of the male industrial population in 

 civilized countries, ami in about one per thousand of females. Among 

 the males of the more highly educated classes, taking Eton boys as an 

 example, the color-blind are only between 2 and 3 per cent., and per- 

 haps nearer to 3 than to 3. Whether a similar difference exists between 

 females of different classes, we have no statistics to establish. The 

 condition of color-blindness is absolutely incurable, absolutely incapa- 

 ble of modification by training or exercise, in the case of the individual; 

 although the comparative immunity of the female sex justifies the sug- 

 •gestion that it may possibly be due to training throughout successive 

 generations, on account of the more habitual occupation of the female 

 eyes about color in relation to costume. However this may be, in the 

 individual, as I have said, the defect is unalterable ; and if the difference 

 between red and green is uncertain at 8 years of age, it will be equally 

 uncertain at 80. Hence the existence of color-blindness among those 

 who have to control the movements of ships or of railway trains con- 

 stitutes the real danger to the public; and it is highly important that 

 the color-blind, in their own interests as well as in those of others, 

 should be excluded from employments the duties of which they are 

 unfit to discharge. 



The attempts hitherto made in this country to exclude the color- 

 blind from railway and marine employment have not been by any means 

 successful. As far as the merchant navy is concerned, so-called exami- 

 nations have been conducted by the board of trade, with results which 

 can only be described as ludicrous. Candidates have been " plucked " 

 in color at one examination, and permitted to pass at a subsequent one; 

 as if correct color-vision were something which could be acquired. 



