CASE OF COLOUR BLINDNESS. 



505 



Contrast Tests. 



A white screen was illuminated by light from two sources — one coloured, the other 

 white — and thus two images of an object, coloured with complementary colours, were 

 thrown side by side on the screen. The first column gives the name of the coloured 

 light and of one shadow ; the second gives the colour of the other shadow. The results, 

 as given by Mr A., are put in brackets alongside. 



Eed (red). 



Eeddish-yellow (reddish). 

 Green (grey). 

 Blue (grey). 



Blue-green (grey). 

 Bluish (grey). 

 Bluish-red (reddish). 

 Yellow (no shadow visible). 



Again, coloured discs, having the same colours as those which were used in the disc 

 tests, were placed on a white background, and were suddenly withdrawn after they had 

 been gazed at for some time. When a green disc was used, Mr A. saw distinctly the 

 reddish after-image. When red, blue, and yellow discs were used, he saw no after-image. 



In this way it is proved that the green colour, though it was grey to him, could yet 

 produce the complementary red colour by contrast. 



Spectrum Tests. 



Colour Nomenclature. — Mr A. was shown a patch of practically monochromatic 

 spectrum colour and was asked to describe its appearance. The results are given 

 below, the normal terms being in the left-hand column and Mr A.'s in the right-hand 

 column. 



Dark red 



Bright red 



Orange-red 



Eeddish-yellow 



Slightly reddish-yellow 



Yellow 



Very yellow-green 



Yellow-green 



Green 



Bright blue-green 



Blue 



Strong dark blue 



Violet 



Dark violet 



Very dark violet 



Darkest visible violet 



Dark red. 



Bright red. 



Eed. 



Warm white. 



Less warm white. 



White. 



White. 



Very nearly grey (mixed with something). 



Very nearly grey (mixed with something). 



Greyish. 



Grey. 



Grey (darker than last). 



Dark grey. 



Darker grey. 



Still darker grey. 



Very dark grey (no red). 



