COLOUR BLINDNESS.

Daily Telegraph (Napier), Issue 3163, 18 August 1881, Page 4

COLOUR BLINDNESS.

Mv Brundenell Carter, F.R.C.S., has commenced a series of Cantor lectures at tho of A rts on colour-blindness. Tn the x ' or preliminary lecture, Mr Carter fir.«t> _ ■-„,} R nd illustrated by experiments the desenu * colour vision and tho constitution nature ot n( j re f en . e fl fc_. e occurrence vf of light; a. ~ to tbe i nsen sibility of the colour- Wincing ; aI Qr comp i ete) to one of retina, either part* of wavo . niOT einent oi tho three velocities osefh It ff> n o w. which white light , nt s three varietiee that colour-blindness ptesv- ___ that of kind, as well as mwy o blinrlness it may ho either oiUia^ es _. olefc> The two to green, or blindness ttho h 'much, more first-named forms are no..' - g fe u fc are also common than voilet blindne.. 'stance', fnnsol inunh greater practical irnpu. -.. ecoffl ;iition much as they interfere with the*i. ~0 , j0 V, .,i of tho coloured lights which are etu_ nll for railway and naval signalling, and w.. _ f according' to the unanimous opinion v. practical men, cannot be replaced for those purposes by any others. In bis second lecture Mr Carter proceeded to explain that the appearance of the world to the colourblind must he less bright, less luminous, than to the colour sighted, and that the appearance of whiteness, as familiar to the latter, must be unknown to the former. Whiteness is the result of the blending of the three primary colours of the spectrum in correct proportions, and tbe colour-Mind, who perceive only two of these primaries, and can consequently only blend two, must gee white surfaces as if their colour were compounded of red and violet, of green and violet, or of red and green, according to the primary which was wanting from the r>er cpph'on's of the individual. Professor Holmgren had lately discovered two cases of one-sided colour-blindness, in one of which one eye was blind to red, in the other to violet, the remaining eye in each person hvaing normal colour perception, or nearly so. By the aid of these persons he had been able to arrive at a better notion of the actual appearance of things to the colourblind than bad been previously obtained, and now the great object was to find, a case of onp-sided green-blindness, by which the inreotiVntion might be rendered complete for all forms of the defect. In each of the two eases referred to it was found that only two of tha primary colours of the spectrum were perceived, the extreme red being in- j visible to one eye of one of the persons and j •h- whole of the violet to one eyo of the i other,