COLOUR-BLINDNESS. 509 
other.-” Orange and yellow were selected easily, and appeared 
very bright to him. 
About six years since, whilst in good bodily health and 
vigour, his sight began to decline, and now, for some months 
past, he has been quite blind. The present appearance of the 
internal eye when examined with the ophthalmoscope is shown 
in figure 2. It is technically called white atrophy — that is, the 
blood supply to the optic nerve and retina is in some way cut off : 
in consequence the vessels are very small and nearly obliterated; 
the choroid coat is sharing the general disorganization. 
These are only a few of the facts which have been brought 
to our knowledge in connection with the very interesting- 
subject of colour-blindness. 
EXPLANATION OF PLATE. 
Fig; 1. An enlarged view of the colour-blind eye free from other defect. The 
outer dark-coloured ring is the iris. On looking through the pupil, 
the circular opening in the iris, with the opthalmoscope, we first see 
a bright pink background, the choroid coat ; this with the optic nerve 
constitutes the fundus oculi. The small and nearly centrally situated 
circular disc observed when the eye is turned a little inwards, is the 
optic nerve, and from its centre issues the vessels of the retina. 
Artery and veins closely accompany each other for a short distance, 
and then divide, first into two branches, one of which, with its 
vein, is seen to proceed upwards, and another pair downwards ; and 
after passing the margin of the optic nerve they diverge, and again 
subdivide, split up into numerous smaller branches, some of which 
come forward to the ciliary processes. The vascular choroid coat 
imparts the pink colour to the back of the eye, which is nearly all 
reflected to the eye of the observer. The only difference observed 
in the eye of the colour-blind is the paler appearance of the fundus, 
or choroid coat, and occasionally whitish interspaces indicative of a 
small and languid blood supply. 
Fig. 2. Shows the internal eye in an advanced state of disease, and is drawn 
from the eye of Mr.-Butcher, who, it will be noticed, suffered from 
colour-blindness years before his disease deprived him of sight. It 
cannot, therefore, be supposed that his colour-blindness was in any 
way owing to the disease which destroyed vision. The pupil is 
nearly fully dilated, forming a part of the diseased condition ; con- 
sequently, a much narrower ring of iris is seen than is given in 
Fig. 1. The fundus oculi , choroid coat, is very deficient in blood, 
which gives the mottled appearance, and indicates a state termed 
atrophy, in which the optic nerve and vessels of the retina is seen 
to share the supply of blood to retina and choroid, being in some 
way impeded, or nearly cut off, probably by a tumour forming in 
the brain in close proximity to the optic nerves. In other respects, 
the gentleman was in good health, and it is impossible at present to 
say to what he can attribute his total loss of sight. 
