172 



COLOUR VISION 



v. Kries found the observed value to be 137, and so on, as in the follow- 

 ing table. 



Wave-length 



of homo- 

 geneous light 



Quantities of 

 670'8 MM and 552 MM 

 in normal match 

 670'S MM 552 M 



Stimulus value 

 for deuteranope 

 Calculated Observed 



From this table we also see that the stimulus value of the yellow- 

 green (552 jLt/x) is to that of the red (670-8 /JLU,) as 101 : 4-9 or about 5 : 1 

 for the protanope, whereas for the deuteranope it is only as 64 : 33 or 

 about 2:1. 



The luminosity of the spectrum. The luminosity curves of dichromats 

 were investigated by Hillebrand (1889) 1 , who found the protanopic 

 maximum at 560 658 /^u, and by Konig and Ritter (1891) 2 . The 

 following table gives the values for two trichromats and three 

 dichromats at the intensity value H. 



Trichromats 



Dichromats 



Protanopes 



X 



0-071 



0-183 



0-517 



0-976 



1-370 



1-477 



1-339 



1- 



0-700 



0-492 



0-250 



Figs. 47 and 48 show the curves. 



Ritter's protanopic curve for the lowest intensity A is almost 

 identical with Konig's. Konig thus early demonstrated the identity 

 of the protanopic achromatic scotopic and the normal achromatic 



1 Sitz. d. Wiener Akad. xcvm. 3, 70, 1889. 



2 Konig, p. 144. 



