CLASSIFICATION OF THE SENSES
We are commonly thought to possess five senses. Actually, there are many
more. We may classify them as follows: 1) the cutaneous senses - touch, heat, cold
and pain; 2) the deeper senses -pressure and muscle sense; 3) the internal senses, or
senses from the internal organs of the body; 4) the special senses, or those in which
the receptors lie in special organs - sight, hearing, equilibrium, taste and smell; and
finally 5) the general body senses - hunger, thirst, fatigue, sexual sensation, etc.
The cutaneous senses. There are said to be 500,000 touch receptors in the skin.
They are unevenly distributed, being most numerous in the finger tips, lips and
tongue, and least numerous on the back. Their receptors are specialized structures
called Meissner's corpuscles. The sense-organs for cold constitute 150,000 receptors;
they are the end-organs of Krause. Warmth has about 16,000 receptors, the endorgans
of Ruffini; and pain has some 3,000,000 receptors. Pain receptors, however,
are not specialized; they are simply the naked ends of the pain nerves, somewhat
branched at their terminals. The Pacinian corpuscles are the receptors for pressure,
and the muscle spindles for muscle sense.
