When examined by polarized light, it seems that on the one hand he did not appreciate the equality of intensity of two complementary colours as did ordinary vision ; but he found a total and abrupt difference when colours passed at once from the finest red to very rich deep blue, a distinction far from being marked to others.
His visual organ was unable to perceive the different mixtures of red which accompany blue to make it pass into purplish violet. This precise circumscription of the consti tutive domain of a colour is a fact which, in the opinion of Professor Wartmann, was new and worthy of being remarked.
Whilst a series of these experiments with polarised light were on, the sun, which had been obscured, suddenly shone out, and D— declared that the colours imme diately assumed a different tint to his sight, all reddening in a sensible manner, so that he called red that which he had before named green and ill-defined blue, whereas the Pro fessor saw no other change in the colours than an increase of their brilliancy and strength.
Wartmann then submitted the patient to experiments to ascertain his perception of the complementary colours, and the result showed that although his eyes were not insensible to them, the colours which appeared to him complementary were not the same as those so regarded by the normal eye. The Professor then painted a human head, giving to each part a complementary colour. Thus the hair and eyebrows were white, the flesh brownish, the sclerotica Wack, the lips and cheeks green. When asked what he thought of the head, D— replied that it appeared to him na tural. that the hair was covered with a white cap little marked, and that the carnation of the cheeks was that of a person heated by a long w&k.
There are a certain number of cases of in sensibility to colours which have been quoted by all writers on the subject. We shall there fore content ourselves with merely referring to them*, describing a few well marked and uncommon instances less generally known.
Dr. Boys de Loury j- has published the particulars of a M. H—, who was obliged, i on account of his defective sight, to aban don the profession of a dyer. His principal colour was yellow. The brilliant yellow of the apricot and deep brown of the chesnut were only distinguished as varieties of shade.
All dark hues were called black ; scarlet ap peared as a blue grey, rose colour dirty white ; orange, pure yellow ; apple green, yellow ; lilac, blue ; violet, grey. There was no un
usual appearance in his eyes, but he saw most perfectly in the evening.
Dr. Sommer* has described his own case thus. Blue can always be distinguished from yellow, bright blue from green, and deep red from black, but green and dark blue are often confounded. Yellow, black, and de cided blue are the fundamental colours. If he holds a leaf of a tree and a stick of red sealing-wax side by side he recognises dis. tinctly the difference in intensity between the two colours, but cannot affirm which is green or which red : rather decided blue and rather intense red bear a great re semblance; blue is confounded with red, green with brown, brown and orange with bright brown. As to crimson, lilac, purple and deep scarlet, they are colours of which he cannot form even an idea. He one day met a lady wearing a blue bonnet ornamented with red roses, but could scarcely distin guish any difference between the two. On another occasion, when walking out it began to rain. " Then (says he) a crowd of red um brellas displayed themselves, and I compared the colour to the azure of the sky." The rainbow appeared to hint composed of blue and yellow ; he knew that there were shades, but could not satisfactorily discern them.
The case of the late Mr. Troughton was examined by Sir John Herschel] and Sir D. Brewster, and it was ascertained that he saw the red space yellow ; hence according to the iews of Sir D. Brewster, he saw a space con taining much yellow, and little blue, the red light being as it were absorbed in consequence of the retina being insensible to its action. Sir D. Brewster goes on to say f, " if this be the case there must have been a diminution of light in the red space seen by Mr. Troughton, and I am persuaded from the experiments I made upon his eyes that this was the case ; but whe ther it was to the extent of the total defalcation of the red rays, I will not venture to assert. But it is not necessary that it should be so ; the defective perception of red light may be accompanied with a more acute perception of the other colours, in a manner analogous to what takes place in the chemical spectrum, where the removal of the red rays produces an increased action of the rays that are left." Sir D. Brewster, adds that he has long been of opinion that the retina receives a more powerful luminous impression from yellow light than from the pure white light of which this yellow forms but a part.