238 WRITINGS OF JOSEPH HENRY. [1845 



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 discrimination of different shades of color not possessed 

 by those otherwise employed. 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, improve- 

 ment of the condition of 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. Professor Wartmann 

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

 perceived in the usual manner, until at the ninth year ; 

 when the boy received a violent blow on the head, which 

 fractured the skull, and rendered a surgical operation neces- 

 sary. 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 pre-disposed to this 

 peculiarity. 



With regard to hereditary pre-disposition 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 gen- 

 erations, both on the maternal and paternal side. The boy 

 before mentioned, as becoming color-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 consisted of individuals with blonde hair, and all the 

 males with defective vision ; the other, of those with red 

 hair and ordinary power of vision. 



