s of the surface, and ask the person whether the
touching body is hot or cold. Test roughly the sensibility of different
parts of the body with cold and warm metallic-pointed rods.

Experiment 126. Touch fur, wood, and metal. The metal feels
coldest, although all the objects are at the same temperature. Why?

Experiment 127. Plunge the hand into water at about 97 degrees F. One
experiences a feeling of heat. Then plunge it into water at about 86
degrees F.; at first it feels cold, because heat is abstracted from the
hand. Plunge the other hand direct into water at 86 degrees F. without
previously placing it in water at 97 degrees F.,--it will feel pleasantly
warm.

Experiment 128. _To illustrate warm and cold spots_. With a blunt
metallic point, touch different parts of the skin. Certain points excite
the sensation of warmth, others of cold, although the temperatures of
the skin and of the instrument remain constant.

245. Necessity for Personal Cleanliness. It is evident that the skin,
with its myriads of blood-vessels, nerves, and sweat and oil glands, is an
exceedingly complicated and important structure. The surface is
continually casting off perspiration, oily material, and dead scales. By
friction and regular bathing we get rid of these waste materials. If this
be not thoroughly done, the oily secretion holds the particles of waste
substances to the surface of the body, while dust and dirt collect, and
form a layer upon the skin. When we remember that this dirt consists of a
great variety of dust particles, poisonous matters, and sometimes germs of
disease, we may well be impressed with the necessity of personal
cleanliness.

This layer of foreign matter on the skin is in several ways injurious to
health. It clogs the pores and retards perspiration, thus checking the
proper action of the skin as one of the chief means of getting rid of the
waste matters of the body. Hence additional work is thrown upon other
organs, chiefly the lungs and the kidneys, which already have enough to
do. This extra work they can do for only a short time. Sooner or later
they become disordered, and illness follows. Moreover, as this unwholesome
layer is a fertile soil in which bacteria may develop, many skin diseases
may result from this neglect. It is also highly probable that germs of
disease thus adherent to the skin may then be absorbed into the system.
Parasitic skin diseases are thus greatly favored