184 PROFESSOR WARTMANN ON DALTONISM, 
from the supposition that the choroid is essential to vision, he 
conjectures that the invisibility of the red colour to daltonians is 
owing to the retina itself having a blue tint, so that the light 
being deprived of its red rays by the absorbent power of that 
membrane, the coloured impression upon the choroid will be 
destitute of red. The same objections drawn from anatomical 
data, and from the influence of the glasses upon the perception 
of colours, would suffice to overthrow this hypothesis, if it were 
not contradicted by facts. We have seen that D * * * and others 
were able to appreciate red in the spectrum. 
According to the phrenologists, the distinction of colours is a 
faculty which does not depend upon the eye, but on a particu- 
lar part of the brain, which they term the organ of colours. 
“ Observation proves,” says Mr. Combe *, “that those indivi- 
duals in whom the portion of the brain which is immediately 
above the eye, beneath the eyebrow, is largely developed, possess 
in a high degree the faculty of distinguishing colours.” It is 
thus the imperfection of this organ which is the origin of dal- 
tonism, and the proof is that those who are affected with it 
possess an ocular apparatus whose mechanical construction and 
optical effects are faultless. 
The Gazette des Hépitaux of October 19, 1839, remarks that 
the first period of amaurosis is accompanied with a confusion of 
colours which, like the natural achromatopsy, appears to depend 
on a diseased state of the brain. In a gutta serena arising from 
hypererethysm, the least vivid colours, such as blue and violet, 
are perceived in the most distinct manner, and yellow objects 
appear red; whilst if the malady is produced by weakness, the 
red light in the end disappears, and does not become visible 
again till the cessation of the morbid state. 
Professor Muncke endeavours to explain the phenomena of 
which we are treating by the following hypothesist. Let us 
suppose that in what concerns the activity of the optic nerve 
there are only two colours with their complementary ones, the 
blue and red with the yellow and green; the first characterized 
by its chemical power, the second by its calorific power; all the 
other colours will be deduced from mixtures and shades of these 
* System of Phrenology. I must say that among the daltonians whom I 
have examined, the organ in question was in general but little evident, except 
in two of them, in whom it was remarkably prominent. 
+ Gehler’s Physikalisches Worterbuch, 2™ Aufg., tome iv. p. 1428; art. 
Gesicht. (Leipsig, 1828.) 
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