. Elementary biology; an introduction to the science of life . Fig. 99. Lateral line in brook trout The line running along each side from the gill cover to the tail is made up of nerve end-organs that are sensitive to certain kinds of vibrations in the water US the feehng of ''A^," just as certain other kinds of vibrations give us the feeling of "; The eye with which we see is an organ whose nerve end- ings receive impres- sions from vibrations in the ether at the rate of from 400,000,000,000 to 800,000,000,000 per second. If the vi- bration is much more rapid or much slo
. Elementary biology; an introduction to the science of life . Fig. 99. Lateral line in brook trout The line running along each side from the gill cover to the tail is made up of nerve end-organs that are sensitive to certain kinds of vibrations in the water US the feehng of ''A^," just as certain other kinds of vibrations give us the feeling of "; The eye with which we see is an organ whose nerve end- ings receive impres- sions from vibrations in the ether at the rate of from 400,000,000,000 to 800,000,000,000 per second. If the vi- bration is much more rapid or much slower, the eye nerves are not affected by them. Sound is a much slower vibration of the air or of solids. Between 16 or 20 vibrations in a second and 25,000 to 40,000 per second the human ear discovers sounds of varying pitch. In the middle register, which includes most of the sounds with which we are familiar, as the pitch of the human voice, the ear can distinguish very slight differences of pitch. It is possible for a trained ear to distinguish more than 1000 shades of pitch in one octave. 282. Perception of other vibrations. Among lower animals the range of vibrations that can be perceived varies considerably; some animals are quite insensitive to soimds of what we would consider the common range of pitch, while some insects can perceive a much higher tone than any human being can hear at all. The earthworm, . 238
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