440 Dr. W. Pole on Colour-Blindness. 



rated " fundamental " energies, corresponding to red, green, 

 and violet, which is essentially the Young-Helmholtz doctrine. 



He describes the phenomena of dichromic vision, according 

 to the testimony of patients (laying some stress on my own 

 case), confirmed by his own experiments and observations. 

 But he prefers to denote the contrasting colours as " warm " 

 and " cold " respectively. 



He then discusses at some length (what is the most im- 

 portant part of his work for our purpose here, namely), " The 

 connexion between the Normal and the Abnormal Systems," 

 and he puts the question thus : — 



Is one of the energies belonging to the normal system wanting 

 in the dichromic system ? Or, in other words, Does every di- 

 chromic system consist of two of the energies of the trichromic 

 system ? 



Maxwell and Helmholtz assumed this ; — and they believed they 

 found it so. 



After discussing at some length the reasonings and calcula- 

 tions of Maxwell and Helmholtz, the author continues : — 



Now do these facts prove that the colour wanting in colour- 

 blindness is generally one of the fundamental colours ? 



We call those colours fundamental which do not spring from 

 others, but are necessary to form others. We assume that every 

 fundamental colour shall base its specific process in definite retina- 

 elements, and in order to characterize it more closely, we determine 

 its subjective luminosity as a function of the wave-length, inasmuch 

 as we presuppose that this will coincide with the intensity of the 

 retina-process. Without regard to colour-blindness we come to 

 the result that the terminal colours of the spectrum, red and 

 violet, and the central, green, are the fundamental colours, as 

 Young had already shown. 



Now it happens that in Red-blindness the wanting colour is 

 not the spectral red, but a red which approaches to carmine, i. e. 

 a red which does not appear in the spectrum, and is only to be 

 obtained by a mixture of two spectral colours, red and violet. 



With Green-blind patients there is reason enough to look for 

 the wanting colour in their neutral spot ; but this by no means 

 decides that the bluish green which corresponds to this neutral 

 must be one of the fundamental colours of the normal system. 



The final result of this, therefore, is that we have no right to 

 consider the colours wanting in the various forms of colour-blind- 

 ness as the fundamental ones of the normal system. 



He adds elsewhere : — 



In a theoretical point of view the simple falling away of one of 

 the energies is inadmissible. It does not harmonize with our idea 

 of the origin of things, that, of three activities which develop 

 themselves in a reciprocal relation as an organic whole, one should 



