346 Report of the Committee on Colour-Vision. 



are two forms of colour-blindness, viz., central or cerebral ; and 

 peripheral, or connected with the optic nerve, as in retro-bulbar 

 neuritis, or in the retina itself, or the choroid. In those cases in 

 which colour-blindness is congenital I can detect absolutely 

 nothing with the ophthalmoscope which would lead me to suppose 

 that the patient was colour-blind. I can, on the other hand, 

 exhibit a number of diagrams showing marked changes in patho- 

 logical colour-blind cases. The portion of the disc affected is 

 more extended, and there is that wedge-shaped triangle on the 

 outer side of the disc which is so characteristic of tobacco and 

 other narcotic amblyopias, only in these cases it is generally more 

 extended. 



[The Witness here handed in a number of charts illustrating- 

 cases of colour-blindness, and called special attention to a pale 

 spot on the retina which was characteristic of such cases.] 



I have brought with me a patient who has perfect colour- 

 vision with one eye, while in the other she has no colour what- 

 ever. She describes the appearance of the spectrum as being 

 like a grey smear. I cannot find that she has any perception of 

 violet. 



Question— -I think you said you had another point to bring before 

 the Committee ? — Yes. I have some information, the result of 

 two or three years' study, which I am not sure exactly regards 

 this Committee, but I have made some experiments showing that 

 if you place glass in front of the eye so as to wholly exclude 

 daylight as far as possible, and have glasses made so that only 

 the blue-violet end of the spectrum passes through, cutting off 

 orange and part of the yellow, the field of vision for white, if 

 contracted, will after a week become enlarged to normal, and that 

 holds good with some cases of detachment of the retina. I was 

 induced to make a large number of experiments with rabbits to 

 ascertain the reason. They were kept in a hutch-like photo- 

 graphic chamber so that no other light than that through the red 

 or blue glass could reach their eyes. After a certain time they 

 were killed and put in a black bag, their eyes being fixed in 

 osmic or nitric acid. I found a distinct anatomical difference 

 between the retinas of the animals under the different glasses ; 

 and these differences come under four heads : — 



Firstly, in the animals kept in the blue light the rods of the 

 retina adhere much more closely to the little processes of the 

 hexagonal prism, so that the retina cannot be easily detached 

 after death. Secondly, the pigment under blue glass is increased. 

 Thirdly, the retinas take up fluid more easily than they do in the 

 opposite colour ; and lastly, not only do they stain much better 

 in the staining fluids, but are also more developed, and seem to 

 increase and multiply more than in the red glass. These four 

 points hold good for all rabbits. It seems to me that animals 

 kept under a constant source of blue wave-lengths have certain 

 changes effected in the retina differing from those under the red 

 end of the spectrum, and that possibly may account for the 



