170 PROFESSOR WARTMANN ON DALTONISM, 
Sir D. Brewster* instances a person, still young, and who 
saw in the spectrum only yellow and blue. When the middle 
of the red space was absorbed by a blue glass she saw the black 
part terminated on both sides by what she called yellow. 
M. Collardo confounded blue with yellow, red with greeny. 
Girod de Chantilly speaks, among others{, of an apothecary 
of Strasburg who with difficulty distinguished colours. He ex- 
plains this anomaly by admitting that there are only three colours, 
and that the retina possesses for the perception of each of them 
a peculiar membrane, which may in certain cases become in- 
active. 
Brandis§ relates of himself, that he cannot distinguish light 
blue from rose-red, that he easily confounds green with blue, 
yellow with red, yellowish red with green in its deep tints, blue 
with red in its light tints. His nephew had been obliged to 
give up a silk trade because he could not distinguish sky-blue 
from rose-red. 
Wardrop || remarks that daltonians perceive a difference in 
colours in general, but without being able to say in what it con- 
sists, or to name the colours separately. According to him, they 
are never mistaken in yellow and blue; all the other colours 
appear to them to be modifications of these. They see in the 
spectrum only yellow and blue. They distinguish with diffi- 
culty the different kinds of green and red; they call vermilion, 
the colours next to yellow, carmine, and other similar tints, which 
they however find yellow by candle-light, blue. It is evident 
that the author has studied but a very limited number of cases 
of daltonism. 
Hig; 
New OBSERVATIONS. 
§ 1. General Remarks. 
Number of Daltonians.—1 have already said that the number 
of persons affected with daltonism is much more considerable 
* Brewster. Edinb. Journ. of Science, vol. vii. p. 85. A Treatise on Op- 
tics, chap. xxxvi. p. 311. (vol. xix. of the Cabinet Cyclopedia. Lond. 1838.) 
+ Journ. de Phys., tome xii. p. 86. 
¢ In a work published in English under the pseudonym of G. Palmer, 
afterwards translated into French with the title of Zhéorie des Couleurs et de la 
Vision, 8vo. 
§ Goethe. Zur Naturwissenschaft und Morphologie, 1 Heft, p. 297. 
|| Essays on the Morbid Anatomy of the Human Eye. London, 1818, vol. ii. 
p-196. Meckel’s Archiv fiir die Physiologie, Ba. v. 
