54 BULLETIN OF THE 



A communication was then read by Mr. Swan M. Burnett, en- 

 titled 



COLOR PERCEPTION AND COLOR BLINDNESS. 



The speaker first gave the Young-Helmholtz theory, which con- 

 sists in the assumption of three fibres in the retina corresponding 

 to the so-called fundamental colors, red, green and violet, stating 

 the objections that have been brought against this theory by Mauth- 

 ner and others, when viewed from the standpoint of color blindness. 



He then explained in brief the theory of Prof. Hering, of Prague, 

 according to which there are supposed to be in the retina three 

 chemical substances, which are called the black-white, the red-green, 

 and the blue-yellow. These are acted on by light, by assimilation, and 

 by dissimilation. Dissimilation (D) of the black-white substance 

 produces white, its assimilation (A) black. The D-action on the 

 red-green produces red, the A-action green. The D-action on the 

 blue-yellow substance produces blue, the A-action yellow. When 

 one of the substances is lacking there is an inability to properly 

 perceive the pair of colors peculiar to it. There is therefore red- 

 green blindness, and blue-yellow blindness. The objections to this 

 theory as advanced by Prof. Donders and others were then brought 

 forward. 



There are two strong objections to both these theories aside from 

 those mentioned, first, their want of simplicity, and second, the 

 necessity of inventing new tissues and novel reactions of tissues to 

 the affecting agent. 



The true theory of colors, when found, we have every right to 

 expect will be simple, and the laws governing it will be in keeping 

 with the action of light on simple substances, and in the opinion of 

 the speaker, they would be found to lie in the direction of the recent 

 discoveries of the action of light on the molecular structure of 

 homogeneous substances, and he accepted as the foundation of his 

 speculations that variation in sensation would have its basis, not in 

 complexity of tissue, but in the varying action of the affecting agent. 



A theory on this basis would have the retina a substance whose 

 molecular structure would be such as to allow it to respond promptly 

 to each of those undulations of the ether corresponding to the prin- 

 cipal colors. The wave length corresponding to red, for example, 

 would produce a molecular change (most probably simply vibratory) 

 which would be carried to the brain centre of vision by the optic nerve, 



