A THEORY OF COLOR-VISION 93 



tion is then that 



en = r (Si — r) cos 9i . (3) 



With this assumption the maximum of a for any stimulation Si occurs 

 for 



cos $! : cos 8 2 : cos 8 3 = S t — r: S 2 ~ ri S 3 — r , 



with r the smaller root of 



6r 2 - 3r 2 Si + 2 S> 2 = . 



A more exact specification of the form of the functions en can be made 

 only by a detailed comparison with experimental facts. 



