FIG. 14.—The prism's analysis of a bundle of light rays. On the right are shown the relation of
vibration rates to temperature stimuli, to light and to chemical stimuli. The rates are given in
billions per second.—After WITMER.The End-organs and Their Response to Stimuli.—Thus the radiations of ether
from the sun, our chief source of light, are so rapid that billions of them enter the
eye in a second of time, and the retina is of such a nature that its nerve cells are
thrown into activity by these waves; the impulse is carried over the optic nerve
to the occipital lobe of the cortex, and the sensation of sight is the result. The
different colors also, from the red of the spectrum to the violet, are the result of
different vibration rates in the waves of ether which strike the retina; and in
order to perceive color, the retina must be able to respond to the particular
vibration rate which represents each color. Likewise in the sense of touch the
end-organs are fitted to respond to very rapid vibrations, and it is possible that
the different qualities of touch are produced by different vibration rates in the
atoms of the object we are touching. When we reach the ear, we have the organ
which responds to the lowest vibration rate of all, for we can detect a sound
made by an object which is vibrating from twenty to thirty times a second. The
highest vibration rate which will affect the ear is some forty thousand per
second.
Thus it is seen that there are great gaps in the different rates to which our senses
are fitted to respond—a sudden drop from billions in the case of the eye to
millions in touch, and to thousands or even tens in hearing. This makes one
wonder whether there are not many things in nature which man has never
discovered simply because he has not the sense mechanism enabling him to
become conscious of their existence. There are undoubtedly "more things in
heaven and earth than are dreamt of in our philosophy."