Bauhaus-Universität Weimar

Titel:
Dictionary of philosophy and psychology including many of the principal conceptions of ethics, logics, aesthetics ... and giving a terminology in English, French, German and Italian, vol. 2 [lead-zwing]
Person:
Baldwin, James Mark
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit29448/816/
VISION 
which are the sources of the sensations of red, 
yellow, and green. The blue sensation is 
furnished exclusively by the visual yellow of 
the rods, and the sensation of a faint light 
(and that of the totally colour-blind) is also 
blue in quality, and is due to the visual 
purple ; hence the fovea, where there is no 
visual purple, is blind to blue (‘Ueber den 
menschlichen Sehpui'pur und seine Bedeutung 
für das Sehen,’ Sitzber. AJcad. TYiss. Berlin, 
1894). The blue-blindness of the fovea has not 
been confirmed by other observers ; it is diffi¬ 
cult to think that the cones can be condensing- 
glasses, and at the same time contain fibres 
of the optic nerve, but that they would have 
to do in order that the effect of photo-chemical 
processes taking place in the pigment epi¬ 
thelium might be communicated to the brain; 
rods and cones are so absolutely alike in 
structure (except for their basilar termina¬ 
tions, Plate I, Fig. 6) that it is unnatural to 
assign to them such unlike functions. 
v. Kries is apparently in the anomalous 
position of believing that grey, when furnished 
by the cones, is a mental reconstitution out 
of the even red-green-blue sensations, but 
that, when furnished by the rods, it has its 
source in some distinctive physiological 
process. 
Donders has a double theory—three-colour 
(with three different cones, to save the 
doctrine of specific energy) in the retina, and 
four-colour, with partial dissociation-processes, 
in the cortex. In his theory (as in Hering’s) 
red and green are complementary colours, 
which is contrary to fact : green has for its 
complementary purple, and the complementary 
of red is peacock, or blue-green; red and 
green mixed together make, not white, but 
yellow. The followers of Hering are able to 
think of red and green as complementaries 
only by choosing a very bluish red (purple) 
or a very bluish green (a full blue-green in 
fact) as the elementary colours ; but this is 
to give up at once the beautiful reliance upon 
our power to distinguish, by immediate intro¬ 
spection, between a ‘mixed’ and a ‘non- 
mixed’ colour, which it is Hering’s great 
service to have brought about. 
The theory of Göller is one of great in¬ 
terest on account of the fact that in it a con¬ 
ception has been devised by means of which 
the process which underlies colour may be 
regarded as an epiphenomenon, so to speak, 
i. e. as something superimposed upon an 
achromatic light-process; the theory makes 
use of the known highly refractive quality 
of the end member of a visual element, and 
of the existence of a peculiar transparent 
thin plate just in front of it, to account for 
light becoming circularly polarized within 
the cones ; the amount of disturbance corre¬ 
sponds then to degree of luminosity, and the 
plane of polarization to the colour. It is an 
impossible theory, because it requires us to 
suppose that molecular disturbances polarized 
in different planes can be propagated as such 
along the nerve-fibres ; but the conception of 
colour as an aspect of a non-specific light 
sensation is not bad. It is, in fact, just what 
is needed by Hering to enable him to regard 
all the brightness of a colour as due to its 
black-white constituent, and as wholly un¬ 
influenced by the presence of the colour- 
character (his idea of the specific brightening 
power of the colours was introduced to ac¬ 
count for the Purkinje phenomenon, and is no 
longer necessary since that is known to be 
merely incidental to the oncoming of adapta¬ 
tion to a faint light: Tschermak); his own view, 
however, that chemical changes are going on 
in colour-substances which are of an exactly 
similar nature to those which take place in 
the black-white substance, and that they 
nevertheless contribute nothing to the total 
volume of the sensation, is very improbable. 
The main objection to the theory of Thomas 
Young, an objection which is insuperable, 
and which lies upon the threshold, is that it 
takes no account of the fact, patent to the most 
cursory observation, that, while a mixture of 
the causes of red, green, and blue is sufficient 
to occasion tbe sensation grey, grey is never¬ 
theless not a red-green-blue sensation. The 
theory is good, inasmuch as it reduces the 
innumerable physiological colour - processes 
supposed to exist in the visual organ by 
Newton to a small number : it accounts 
admirably, for instance, for the fact that all 
the successive homogeneous light-rays between 
X 505 and X 470 furnish no new sense-quality, 
but only a series of blue-greens gradually 
varying in the relative amount of each con¬ 
stituent sensation : this is just the sort of 
theory that the psychologist demands—the 
physiological conception offered mirrors cor¬ 
rectly the deliverances of consciousness. And 
the same thing holds for the bluish-reds and 
the reddish-blues. But when we are asked 
to admit that in the third side of the colour- 
triangle the case is still the same, that what 
we call greenish-yellows and reddish-yellows 
are in reality, in this same sense, greenish- 
reds or reddish-greens, consciousness rebels ; 
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