The Newton tradition - Duplicity Theory of Vision - page 11

of a medium between the objects and the eye was necessary for seeing
the objects. In fact, Aristotle assumed that movement of a medium
was also a necessary condition for the sensation of sound, smell,
touch and taste (see Goethe, 1810 , p. 533-534).
2.3 P h o t o t r a in s d u c t i o in i in t h e r e t i in a
a n d s i g n a l t r a n s m i s s i o n t o t h e
brain:Newton's speculations
In his attempt to explain the strict connection between rays and
colour, Newton ( 1675 ), in his second paper on light and colour,
suggested that the rays excited vibration in an ethereal medium when
they impinged upon the ends of the capilamenta of the optic nerve
in the retina. Depending on the size and strength of the rays, they
were thought to excite vibrations of various sizes. As the rays became
bigger and stronger, the vibrations became larger. These vibrations,
then, were thought to run through the optic nerve (as the corpuscles
themselves could not do) to the sensorium and there affect the sense
with various colours according to their size and mixture. The largest
vibrations produced red, the middle green, and the smallest violet,
while white could be generated by mixing all the different vibrations
in due proportion. No interaction between the ethereal waves and
no change in quality occurred in the optic nerve. Thus, the different
qualities of colour seen were assumed to depend on the interpreta-
tion made by the sensorium.
Interestingly, Newton hypothesized that the vibrations of the
retina and the eardrum were conveyed to the sensorium by similar
processes. In fact, he speculated that all types of sensation were
transmitted by vibration of the ethereal medium (see Newton, 1730 ,
p. 353). Thus, it appears that Newton anticipated Johannes Müller's
famous 'specific nerve-energy' doctrine by more than 100 years.
Indeed, he correctly attributed the different types of sensory quality
to the brain, and not to activities of nerves leading to the brain, as
Johannes Müller's doctrine most often has been read. It seems fair
to add, however, that Johannes Müller did not take a firm stand on