COLOR BLINDNESS. 199 



SO far as we kuow, to Europe, with the exception of two cases described 

 by Dr. Hays, of Philadelphia, in the Proceedings of the American Philo- 

 sophical Society. It has also as yet been found only amoug the white 

 race, although sufficient observations have not been made to render it 

 probable that it is confined to this variety of the human family. The 

 question has been asked, whether there is any external sign by which 

 to detect, with simple inspection of the visual organ, a case of color- 

 blindness. Professor SYartmann remarks, that he would not venture to 

 give an answer to this question in all cases in the negative. I have 

 observed, says he, in the case of Daltonians whose eyes are brown, of 

 the color which the English call hazel, a golden lustre of a peculiar 

 tint, when the eye was viewed under an incidence of some obliquity. 



Color-blindness is found much more common among men than women. 

 Out of one hundred and fifty registered cases, there are but six of females, 

 and one of these is doubtful. It has been conjectured that needle-work 

 on a variety of colored articles, might be the means of counteracting the 

 tendency to this defect, as well as to produce a delicacy of discrimina- 

 tion of different shades of color not possessed by those otherwise em- 

 ployed. But, in answer to this, it has been remarked, that in the case 

 of Daltonians engaged in painting, there has been found but little, if any 

 improvement of condition of the vision ; and the very employment of the 

 females on works which require a constant comparison of color, would 

 daily reveal cases of blindness of this kind, did it frequently exist in the 

 female sex. This peculiarity of vision is principally congenital. Pro- 

 fessor W. has found but two exceptions. In one of these, colors were 

 perceived in the usual manner, until at the ninth year, when at that time 

 the boy received a violent blow on the head, which fractured the skull, 

 and rendered surgical operations necessary. The fact, however, that 

 three of the brothers of this individual were affected with the same kind 

 of vision, renders it probable that he was constitutionally predisx)osed to 

 this peculiarity. 



With regard to hereditary predisposition there are some persons in 

 whom this defect of vision occurs, whose relatives have never been 

 known to be affected with it: others appear to have inherited it from 

 their fathers through several generations, both on the maternal and 

 paternal side. The boy before mentioned, as becoming blind at the age 

 of nine years, was the eldest of eleven children, seven males and four 

 females ; these were singularly divided into two sets, one of which con- 

 sisted of individuals with blond hair, and all the males with defective 

 vision ; the other, of those with red hair and ordinary power of vision. 



Dr. Seebeclj, as well as Professor Wartmann, has made a series of 

 experiments to determine whether a person of this peculiarity of vision 

 possesses the power of perceiving diflerences in colors which appear 

 identical to us. The result of the investigations of both these philoso- 

 phers was that he does not. Another problem has also been solved by 

 the last-mentioned gentleman, in reference to the difference between a 

 person with this defective vision, and oneof ordinary conditioned sight, in 



