137 
to certain Colours. 
fier's'book of colours by Syme ; but by candle-light this error 
was detected, and the colours were called red with a tinge of blue. 
Black, which is the negation of all colour, could not be distin- 
guished by him from a bottle-green colour, in one instance, 
though the difference was quite obvious to myself. Black, white, 
and yellow bodies are, however, recognised with tolerable cer- 
tainty ; though the shades of white, which again is but the beam 
of all colours, are not distinguishable. The shades of green 
can be distinguished from each other, as already stated, though 
none of them are known from orange. Duck-green, he called a 
red, and sap-green an orange colour. If he closed one eye and 
looked with the other, the results were not altered. His health 
has been good. This defect has not sprung from disease, it 
bears no relation to nyctalopia or amaurosis only in its probable 
seat ; it is natural, not morbid. 
Description qf Eyes . — Mr R. Tucker’s eyes appear to be very 
well formed, being oblate spheroids with cornese, neither re- 
markably convex nor flat. Irides light ash-colour. His vi- 
sion is exceedingly acute. It has been frequently exemplified in 
finding bird’s nests, in shooting small birds, and in reading mi- 
nute print at a short or long distance. Light appears to him as 
light. He sees the forms of surrounding objects like other peo- 
ple at noon-day, in the twilight, and at night. In short, his 
sight is remarkably good in any light or at any distance. His 
grandfather, on his mother’s side, seems not to have possessed 
the faculty of distinguishing colours with accuracy. 
General Remarks . — Physiologists may speculate in opinion, 
whether^or not this deficiency in the faculty of perceiving colours, 
as exemplified in the instance of Mr R. Tucker, depended 
on the eye as the' instrument and organ of vision, or on the 
sensorium to which all impressions made on the retina of the eye 
are referred, and in which the faculty or power of discriminat- 
ing colours is supposed to reside, Vision, regarded as a sensa- 
tion, is only one medium of communication, which the brain or 
common sensorium has with the external world. The other senses 
afford other media. If an eye sees objects clearly, distinctly, 
and quickly, vision cannot be considered defective. The facuL 
ty, whatever it may be, wheresoever it resides, of discriminating 
the differences betweeo different objects, certainly is not confined 
