190 3.] Dr W. Peddie on Theory of Colour Vision. 
449 ' 
colour blindness must be regarded as due to suppression of one 
complementary pair of sensations, while variations in normal eyes 
are due to partial suppression. In this way the sensation curves 
for different eyes may have greater fixity as regards form — de- 
pending on wave-length — than in the trichromatic set. This result 
is desirable if the sensation curves are to be regarded as really 
corresponding to physiological stimulation produced photo-chemi- 
cally or photo-electrically. A simple theory of such stimulation is 
given, and .shown to lead to the required form of relations between 
the four fundamentals. 
(. Issued separately August 3 , 1903 .) 
