Biology Reference
In-Depth Information
the triplicity in the retina. This profound new insight deserves to be
ranked as
the second major paradigm shift in vision research
.
2.8 H e l m h o l t z : t h e Y o u n g - H e l m h o l t z
colour theory
Helmholtz (
1867
) immediately accepted the colour-mixture data of
Maxwell and, as a consequence, the trichromatic colour theory of
Young (
1807
). He summarized its main theoretical statements as
follows (Helmholtz,
1867
, pp. 291-292):
1.
There exist three different types of nerve fibre in the eye. Activation of
one gives rise to red sensation, the other green and the third violet. (In
this statement Helmholtz extended the specific nerve-energy doctrine of
Johannes Müller (
1840
) to a doctrine of specific fibre energy operating
within a single sense organ.)
2.
The three types of fibre are activated to different degrees by different
wavelengths in that red-related fibres are most strongly activated by the
longest wavelengths, the green-related fibres by middle wavelengths,
while the violet-related fibres are most strongly activated by the shortest
wavelengths.
3.
Pure yellow results from moderate activity in red- and green-related
fibres and a small activation of violet-related fibres, while blue is
produced by moderate activities of green- and violet-related fibres
and a small activation of red-related fibres. Finally, white sensation is
produced when the three different typses of nerve fibre are activated to
about the same degree.
4.
The nerve activities of the three different types of fibre are qualitatively
different and transmitted to the brain without interacting with each
other.
As an alternative possibility, Helmholtz (
1867
, p. 292) pointed
out that the triplex mechanism might be based on three independent
and qualitatively different processes
within each fibre.
. Under this
alternative, an essential cause of the triplicity and colour quality
would be seated in each nerve fibre.
Later, in the 1896 edition of his 'Handbuch', however, he,
in accord with Newton (
1675
,
1730
), attributed the different types
