164 



Dr. F. W. Edridge- Green. [Nov. 15, 



1 and 2 cycles per second. It may be as slow as - 6 cycle per second ; or as 

 fast as 2 - 5. In asphyxia the rate which obtained at the point of commence- 

 ment may be triplicated before the attainment of the complete effect. Thus 

 a rate of 1 cycle per second may become one of 3*4. In normal narcosis 

 progression the rate of rhythm may vary considerably in the same individual 

 on different occasions. 



Trichromic Vision and Anomalous Trichromatism. 

 By F. W. Edridge- Green, M.D., F.E.C.S., Beit Memorial Besearch Fellow. 



(Communicated by Prof. E. H. Starling, F.K.S. Received November 15, 1912, — 



Read January 23, 1913.) 



(From the Institute of Physiology, University College, London.) 



Definitions. 



A. Trichromic Vision. 



The trichromic in my classification of degrees of colour-perception are those 

 who have only three colour sensations — red, green, and violet. They see only 

 three colours in the bright spectrum and describe it as consisting of red, 

 red-green, green, green-violet and violet. They apply the designation red- 

 green to the orauge and yellow regions of the spectrum and green -violet to 

 the blue region. 



There are many degrees and varieties of trichromic vision (1, 2, 3, 4, 5). I 

 have classified the colour-perception of individuals as dichromic, trichromic, 

 tetrachromic, pentachromic, hexachromic, and heptachromic. This classifica- 

 tion is made by estimating the number of definite colours seen in a bright 

 spectrum, and the persons belonging to each class behave in every way as if 

 they possessed the number of colour sensations indicated. On my theory of 

 colour-vision each colour sensation is separate and distinct and not compounded 

 of two or more fundamental colour sensations. For instance, there is the 

 strongest evidence that yellow is a simple sensation (18, 24, 25, 26) and that 

 spectral yellow light does not excite the red and green sensations. 



B. Anomalous Trichromatism. 



The term anomalous trichromatism is used in the sense of the Young- 

 Helmholtz theory in which all colour sensations are supposed to be made up 

 of different proportions of three fundamental sensations. A trichromat on 

 this theory is therefore a person with normal colour-perception. An 



