PROBLEM OF COLOR VISION—DANE. 623 
observations upon the color blind. The absence of the green sub- 
stance would not shorten the spectrum, but the lack of the red or blue 
would cut off their respective ends. All of these features are equally 
well explained if, instead of the absence of one of the three sub- 
Fic. 5.—A modified diagram of the Young-Helmholtz theory, after 
Kenig. 
stances, such a modification of its reaction is assumed as would 
be illustrated by a lateral shifting of its curve in the diagram. Thus 
in red blindness the 
red curve is shifted to | | 
"4 Fi ~{ r 
cover more cts the lt. 
in green blindness the ea 
pencil mat Le 
the red; and in the 9 <aagll Ls 
blue blindness the blue ell 
sae cuevesiare b ll Mh 
brought together. Thus Bo. x G B Vv 
in the color blind all 
three substances are Fic. 4.—Diagram to illustrate the Young-Hemholtz theory. 
present but in modified roles sreen, and blue perceiving substances, 
form. Since this modi- 
fied Young-Helmholtz theory accords so well with observations on 
color blindness, it is generally considered as the most satisfactory ex- 
planation of color vision. 
An interesting attempt has been made by Patten to bring this 
theory into relation with structural elements in the cones.*. He be- 
. lieves that the 
visual cells of 
invertebrates 
are character- 
ized by a fib- 
rilletaom 
which is trans- 
verse to the di- 
rection of the 
aM) incident light 
R 0 Y G B V waves, and 
that the ten- 
dency of the 
vertebrate 
rods and cones to seperate into transverse disks is evidence of a similar 
structure. Many hundreds of such fibrils may exist in a rod or cone. 
They are not supposed to vibrate like tense strings, but to act as “ con- 
ductors or resonators,” a fact which would not exclude chemical 
“Patten, W. A basis for a theory of color vision. Amer, Nat., 1898, vol. 32, 
pp. 833-837. 
