362 STUDIES IN SPECIAL SENSE PHYSIOLOGY 



Precisely similar results were obtained in matching spectral 

 colours. 



Polariscopic Matches (Hering). 

 Yellow Glass. Blue Glass. 



The analogy between normal vision under conditions of dark 

 adaptation and the vision of the totally colour-blind will also be 

 apparent from the next two tables. The first gives the intensity 

 values of the different parts of the spectrum for a normal " dark " 

 eye, as determined by Schaternikoff ( 13 ), and the second Abney's 

 observations ( 14 ) on two other cases of total colour-blindness. The 

 units of intensity in the two cases are not comparable, but it 

 will be observed that the two maxima occur in the same 

 part of the spectrum. 



" Twilight " Values of a Spectrum (Schaterniko/). 



