Discovery of his Theory of Colors. 253 
“Pure red excites strongly the fibers sensitive to red, and 
feebly the two other kinds of fibers ; sensation, red. 
1. 
i tee 
sorts faateseo 
2 i toa Po 
sees 
| __ 
are 
R e) 18 + Vv 
“Pure yellow excites moderately the fibers sensitive to red and 
to green, feebly those fibers sah oa to violet ; sensation, yellow. 
ure green excites strongly t ers sensitive to green, 
feebly those sensitive to red and to violet sensation, green. 
ue excites in a moderate degree those fibers sensitive 
to green and to violet, feebly those sensitive to red ; sensation, 
ue. 
‘Pure violet excites strongly those fibers specially destined 
to receive this sensation, and the other fibers are feebly affected 
by this light ; sensation, violet. 
“The nearly equal excitation of all of the fibers will give the 
sensation of white, or of whitish col 
“The choice of the three fundamental colors is 
to some extent arbitrary. We can choose at will any three 
colors whose mixture produces white. Young no doubt was 
guided by the consideration that the extreme colors of the spectrum 
occupied the privileged positions.* If we do not choose these 
colors, we must take for one of the colors a purple tint, and the 
curve which responds to it in the figure will have two maxima: 
one in the red, the other in the viglet. The het sa Poles ee 
out being an impossible one, will be more comp. 
as I know of, there exists no means of deertajing diretly te 
fundamental colors but He examination of persons affected w 
color blindness. We will subsequently see how far that peiire 
red is cone eae the bicubic of Young, at least so far as the 
red is red.” 
3 
is n general, then, light which ere of undula- 
on - different wave-len gths pr roduces diffe mpressions 
n our eye, namely, Te of farce bition es the num- 
an of hues which we can recognize is much smaller than that 
of the various possible Sceabinateus of rays with different wave- 
lengths which external objects can convey to our eyes. 
*The writer has italicized the above for the purpose of a future reference to it. 
