It was found that—
165 (U) + 48 (R) + 147 (G) = 75 (W) + 285 (B).
The black reflected 3·4 of white; hence the true equation is—
(i). 165 (U) + 48 (R) + 147 (G) = 84·7 (W) + 275 (B).
(ii). 120 (U) + 240 (Y) = 196 (W) + 164 (B) (corrected)—
With 260 (U) + 100 (Y) he sees blue.
250 (U) + 110 (Y) he sees light-blue.
242 (U) + 118 (Y) he sees no blue.
This last in connection with (ii) shows that his blue perception is neutralised by the yellow, although the yellow to him was matched with white.
I have already shown you a chart of the insensitive area of the retina found in a tobacco-blind case, and it may be advisable that you should see an example of the curtailment that exists, both for light and colour, in the field of vision of eyes in which there is progressive atrophy of the optic nerves. The large black area shows the part of the field that was encroached upon. The dark spots show small areas which are also insensitive. The field for colour shown by the inner shaded area is also encroached upon, and practically the patient was blind in a great part of his field. His form vision was also very bad, and his colour perception feeble. The three charts given in these lectures were brought by Mr. Nettleship, for the information of the Colour Vision Committee of the Royal Society, and by his permission they are reproduced here.
Fig. 38.
