492 Capt. W. de W. Abney. Examination for [May 14. 



The examination of these three cases was conducted at different 

 times, the first partially in the presence of the Colour Vision Com- 

 mittee by Mr. Nettleship, and the two last, and part of the examination 

 of the first, at different times, in my laboratory, with the assistance 

 of Mr. Nettleship. 



In all three cases the examination made was an ability to distin- 

 guish colour, luminosity of the different parts of the spectrum, and 

 total sensation of light ; and, in addition, in the first case, to range of 

 colonr sensation on the retina. 



Case I. This patient, Alfred C., aged 36, a traveller, was suffer- 

 ing from rather severe tobacco amblyopia, and was brought to the 

 Committee by Mr. Nettleship. The scotoma was a very marked one, 

 and the loss of colonr sensation most complete. Mr. Nettleship has 

 kindly added the following remarks on the case : 



His acuteness of vision was / with R. and -/ 5 with L. He smoked 

 half-an-onnce of "shag" daily and drank about four pints of beer. His 

 sight had been failing for about two months. As is common in early 

 stages of this disease, the ophthalmoscope revealed no decided changes 

 at the optic discs. 



He was tested at the Royal Institution by Mr. Nettleship, in the 

 presence of the Committee, with the following results : 



He passed the test of the Holmgren wools satisfactorily, proving 

 that the usual vision was normal for colour. I had prepared small 

 pellets of moulder's clay, each weighing 4 grains, and about \ inch 

 in diameter, and had had sets coloured with the same colours as those 

 of the Holmgren wools. C. was told to pick out the blues, reds, and 

 greens. The blue pellets he picked out without fail, and he never 

 made the least mistake in his choice, but he failed entirely to distin- 

 guish the greens or reds, mistaking them for drabs and greys, which 

 were amongst the pellets. When told to look away some 20 from 

 the slab on which the pellets were placed, he at once saw all the 

 colours, but directly he turned his eyes to pick them out, all colour 

 perception, except for blue, disappeared. This test indicated that he 

 had lost all perception of green and red in the central part of the eye. 

 He was next tested with small discs of different colours by Mr. 

 Nettleship, keeping his eye fixed on a given point, and the loss of 

 colour sensation for all except blue, and perhaps a little yellow, in the 

 central part of the eye, was at once made apparent ; the blue he would 

 distinguish with the greatest facility, and the sensation was appa- 

 rently as strong as in normal eyesight. A further test was made by 

 Mr. Nettleship with coloured lights to imitate signal lights, and he 

 named a brilliant red light, and an equally brilliant green light, when 

 side by side, both as white (see also p. 85). 



This man attended at my laboratory, at the meeting of the Com- 

 mittee on Colour Vision, with Mr. Nettleship, and he was tested with 



