(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. [Illustration: FIG. 38. _Left Eye._ _Right Eye._] Two other cases I may give in some detail, one in which the sensation of colour is totally absent in the left eye, the right eye being normal; and the other in which there is colour blindness of a very rare character. The first case is that of a lady, whom we will call Miss W. It appears from the history of this lady that she had a slight stroke of paralysis which affected her left side, and that she subsequently found her left eye was deprived of all sensation of colour. It is said by the specialists who examined her retina that this is a case of atrophy of the optic nerve. She had very little difficulty in matching the most brilliant spectrum colours with the white patch of light. Her curve of luminosity is given in Fig. 39 (see table, page 228). At 19 of the scale, which is well in the blue, she had very little sense of light, though her extinction curve shows that it extended to some distance beyond. The eye in which normal vision existed was, during the examination of the defective eye, bound up with a handkerchief, and when occasionally she was allowed to use both eyes, her astonishment was great to see the colours which she had matched with the white. The curve of luminosity taken with her right eye coincided with my own, which throughout we have taken as normal. From her extinction curve we gather that there was a marked diminution of sensitiveness to light in her left eye compared with that of normal vision. Apparently, in that eye she only has 1/25 of the normal sensitiveness to light near E in the green, but her extinction curve takes the same general form as that of the normal eye. The difference between the sets of ordinates