an all-wise Creator.

316. Muscular Sense; Sense of Temperature; Pain. When a heavy object
is laid upon certain parts of the body, it produces a sensation of
pressure. By it we are enabled to estimate differences of weight. If
an attempt be made to raise this object, it offers resistance which the
muscles must overcome. This is known as the muscular sense. It
depends on sensory nerves originating in the muscles and carrying
impressions from them to the nerve centers.

The skin also judges, to a certain extent, of heat and cold.
These sensations can be felt only by the skin. Direct irritation of a
nerve does not give rise to them. Thus, the exposed pulp of a diseased
tooth, when irritated by cold fluids, gives rise to pain, and not to a
sensation of temperature. Various portions of the body have different
degrees of sensibility in this respect. The hand will bear a degree of
heat which would cause pain to some other parts of the body. Then, again,
the sensibility of the outer skin seems to affect the sensibility to heat,
for parts with a thin skin can bear less heat than portions with a thick
cuticle.

Experiment 139. _To illustrate how the sense of touch is a matter
of habit or education_. Shut both eyes, and let a friend run the tips of
your fingers first lightly over a hard plane surface; then press hard,
then lightly again, and the surface will seem to be concave.

Experiment 140. Cross the middle over the index finger, roll a
small marble between the fingers; one has a distinct impression of two
marbles. Cross the fingers in the same way, and rub them against the
point of the nose. A similar illusion is experienced.

Experiment 141. _To test the sense of locality_. Ask a person to
shut his eyes, touch some part of his body lightly with the point of a
pin, and ask him to indicate the part touched.

As to the general temperature, this sense is relative and is much
modified by habit, for what is cold to an inhabitant of the torrid zone
would be warm to one accustomed to a very cold climate.

Pain is an excessive stimulation of the sensory nerves, and in it all
finer sensations are lost. Thus, when a piece of hot iron burns the hand,
the sensation is the same as when the iron is very cold, and extreme cold
feels like intense heat.

317. The Organ of Taste. The sense of taste is located chiefly
in the tongue, but may also be referred even to the regions of the fauces.
Taste, like touch, con