142 COLOR-BLINDNESS IN ITS EELATION TO 



and which at the time intensely excited public attention, testimony 

 was adduced which led me to suppose that color-blindness was one of 

 the principal causes of the disaster. This impressed me with the idea 

 that official scrutiny and control should be exercised over the sense of 

 color amongst railway employes. Without knowing what had been 

 done or written with reference to this in other countries, I considered it 

 my duty to take the initiative. After convincing myself that the steps 

 to be taken should consist, with the preservation of the existing system 

 of signals, in eliminating from the railway service all employes afflicted 

 with color-blindness, or at least those with certain kinds and degrees, I 

 regarded it, first, of the highest importance, to have a practical method 

 which should render the discovery of the color-blind rapid and certain, 

 without incurring heavy expense or requiring extensive preparations, 

 and in consequence to be able to examine easily a considerable number 

 of individuals. Then it seemed to me essential to endeavor to interest 

 the high functionaries at the head of the railways personally in the 

 matter. 



As regards the method, I had already found one purely theoretic, 

 which, while in agreement with that of Young-Helmholtz, proved to be 

 practical in the examination of the color-blind. But this method was 

 only intended for discovering the types of partial color-blindness (com- 

 plete, according to the theory), but not the form of blindness I had 

 ascertained by the periraetrical examination of the colored visual field, 

 and defined under the name of incomplete color-blindness. The method 

 received accordingly a new practical aim, and it became necessary, in 

 consequence, to render it more accurate, and especially to make a trial 

 of it by an examination of the masses, so as to determine, by experiment, 

 the practical value of the method, and form an idea of the amount of 

 color-blindness in our country, of which no one had the slightest con- 

 ception. The desired occasion presented itself in the mouth of June, 

 1876, and I am indebteded to the politeness of Major-Gen eral Von Kiior- 

 riiig and Major Eudbeck for permission to examine 2,220 men belonging 

 to a regiment of infautrj', cantoned in Upland (standing army and mili- 

 tia), and to the dragoons of the guard (militia). The method proved to 

 be capable, in its extraordinary simplicity, of perfectly answering the 

 end in view with reference to rapidity and accuracy. The examination 

 of each man required, on an average, one minute, sometimes more and 

 often less ; and with the improved form we had given the method, we 

 also discovered, with accuracy, every individual incompletely color- 

 blind. With regard to the knowledge acquired by this examination of 

 color-blindness amongst the population of the province, we found that 

 out of 2,220 men eleven could not distinguish red, seventeen green, one 

 violet (?), and thirty-one were incompletely blind, according to the 

 classification I had used. There were, then, in all, sixty color-blind, 

 or 2.7 per cent. -^The instances of a feeble sense of color are not in- 

 cluded in this. 



