126 Mr. B. Brudenell Carter 



[May 9, 



engine drivers and mariners. The avoidance of collisions at sea and 

 on railways depends largely on the power promptly to recognise the 

 colours of signals; and the colours most available for signalling 

 purposes are red and green, or precisely those between which the 

 sufferers from the two most common forms of colour-blindness are 

 unable with any certainty to discriminate. About thirteen years ac^o 

 there was a serious railway accident in Sweden, and, in the inve's- 

 tigation subsequent to this accident, there were some remarkable 

 discrepancies in the evidence given with regard to the colour of the 

 signals which had been displayed. Prof. Holmgren, of the University 

 of Upsala, had his attention called to this discrepancy, and he found, 

 on further examination, that the witness whose assertions about the 

 signals differed from those of other people was actually colour-blind. 

 From this incident arose Prof. Holmgren's great interest in the sub- 

 ject, and he did not rest until he had obtained the enactment of a law 

 under which no one can be taken into the employment of a Swedish 

 railway until his colour-vision has been tet-ted, 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 laboui's of Dr. Joy 

 Jeffries, of Boston, by several of the United States; while at the 

 same time much evidence has been collected to show the connection 

 between railway and marine accidents and the defect. 



It has been found, by very extensive and carefully conducted 

 examinations 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 colour-blindness exists in a noticeable degree, 

 as I have already said, in about four per cent, of the male industrial 

 population in civilised countries, and in about one per thousand of 

 females. Among the males of the more highly educated classes, 

 taking Eton boys as an example, the colour-blind are only between 

 two and three per cent., and perhaps nearer to two than to three. 

 Whether a similar difference exists between females of different 

 classes we have no statistics to establish. The condition of colour- 

 blindness is absolutely incurable, absolutely incapable of modification 

 by training or exercise, in the case of the individual; although the 

 conaparative immunity of the female sex justifies the suggestion that 

 this may possibly be due to training throughout successive generations, 

 on account of the more habitual occupation of the female eyes about 

 colour in relation to costume. However this may be, in the indi- 

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

 between red and green is uncertain at eight years of age it will be 

 equally uncertain at eighty. Hence the existence of colour-blindness, 

 among those who have to control the movements of ships or of rail- 

 way trains, constitutes a real danger to the public ; and it is highly 

 important that the colour-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. 



