BY JOHN THOMSON, M.B. 89 



One (1) bright red, skein 33 ; one (1) red orange, skein 37 ; 

 three (3) rich orange, skein 39 ; and one (1) yellow, skein 40, 

 were selected by examinees in quest of green. The same ex- 

 aminee 18, selected skeins 37, 39, and 40. Some in quest of 

 red, made selections from among the greens ; one (1) chose 

 skein 3, a blue-green ; three (3) chose skein 5, a medium olive 

 green ; one (1) chose skein 7, a blue-green ; the same examinee, 

 13, choosing skeins 3, 5, and 7 ; that is to say, four (4) green- 

 blind included reds in their choice, and three (3) red-blind, 

 included greens. 



No pink or group 2 selection was made among the reds, 

 and no red or group 3 selection from among the pinks. 



There is no difficulty in detecting a colour-blind individual ; 

 he usually betrays himself before he even makes a selection, 

 by taking the test skein in his hand turning it over and over 

 and examining it as if he hoped to obtain some inspiration 

 through another faculty than that of sight. This is often very 

 marked. But I find a very great difficulty in classifying the 

 colour-blind, and I ought not to, seeing how definite (?) are the 

 directions and exact (?) the colour cards indicating different types 

 of colour blindness. 



It is quite in doubt what a colour-blind man sees, for he 

 cannot communicate his perceptions otherwise than by sugges- 

 tion and when he uses certain terms, say rea or green, there is no 

 evidence that his impressions are similar to ours with reference 

 to these particular colours for he confounds them. 



Two notable cases are recorded by Hippel and Edridge 

 Green of patients who had normal colour perception in one eye 

 and were colour blind in the other. In both instances they 

 recognised the extremes of the spectrum ; Hippel's case saw 

 yellow and blue, Green's saw red and violet but confounded 

 yellow and blue. 



None of my cases confounded the ends of the spectrum, 

 reds with violets, and this is in support of Gladstone's finding 

 with reference to Homer's colour perception and in keeping 

 with Edridge Green's theory of the evolution of the colour 

 sense. 



With the colour-blind a great deal of guessing goes on 

 when selections are being made, and although the defect will 

 invariably assert itself, for one or more of the confusion 

 colours will always be chosen, there will certainly be a variety 

 in the skeins selected and no two examinations will give the 

 same result. 



