Report of the Committee on Colour-Vision. 347 



reason that I find the field of vision increased in almost all cases 

 of patients whose field of vision has been contracted beforehand, 

 if kept for a length of time wearing the goggles I have referred 

 to. I am not prepared to say whether if the rabbits are exposed 

 to ordinary light the retinas would return to their former con- 

 dition. 



Question — It is said that photographers suffer from working 

 constantly in a red light ; do you think that is so ? — No ; but I 

 think they suffer from bad ventilation, as a rule. 



Question — You say that after death there is more difficulty i.i 

 the detachment of retina after keeping the animals in a particular 

 light ; would that have any application to colour-blind cases, or 

 point to any cure ? — I cannot positively state an instance of a 

 detached retina going back, but in almost all cases of slight 

 detachment of the retina, where the field of vision has been cut 

 off over a certain area, that area has been considerably increased 

 after wearing blue glasses, except when separated by effusion 

 and forms of umbrella detachment, when the retina becomes, as it 

 were, bleached. 



Question — Have you had any experience with progressive 

 atrophy, as to whether persons suffering from it have a lack 

 of colour-sensation ? — I find their field of vision, both for white 

 and for colours, is extremely contracted, and that nothing I 

 have ever tried for them has done the slightest good. I have 

 taken the field of vision for a great many atrophies, and find 

 blue is the last colour to disappear, as well as the most extended. 

 I have never found a patient with a blue field and no other, but I 

 have found blue extends further than any other. According to 

 Herring, the blue and yellow field ought to be co-terminous, but 

 [ do not find that to be the case. 



Evidence of Dr. Ediudge Gkeex. 



The Chairman : I believe you have paid a good deal of atten- 

 tion to the question of colour-vision, and perhaps you will be so 

 good as to describe to the Committee the methods you have used 

 in your colour tests, and the general character of the results 

 obtained ? — [Witness handed in a diagram illustrative of psycho- 

 physical colour-perception, and explained as follows] : — 



The theory is that the perception of colour is a perception ( f 

 difference ; colours are confused by the colour -blind, not because 

 of any loss of substance, but because the individual cannot 

 perceive any difference between the rays of light included 

 in a portion of the spectrum which appears monochromatic 

 to him. The size of the monochromatic band varies with 

 the individual. A person who has very defective colour-perception 

 has a monochromatic band so wide as to include several coloui sj 

 which are easily distinguished by a normal sighted person. 



