e adhesion of the lids, which is liable
to occur upon slight inflammation. 2d. In the ears, where the unctuous
wax not only preserves the membrane of the drum and the passage of the
ear moist, but also, by its bitterness, prevents the intrusion of
small insects.

654. The use of the perspiratory glands is to separate from the blood
that portion of the waste matter which is carried off through the skin
in the form of vapor. Sanctorius, a celebrated medical writer, daily,
for thirty years, weighed himself, his food, and excretions. He
estimated that _five_ of every _eight_ pounds of food and drink passed
from the system through the many outlets upon the skin. Many place the
estimate much lower. All physiologists agree that from twenty to forty
ounces of matter pass off from the skin of an adult every twenty-four
hours.

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652. What prevents the evaporation of the water of the cuticle? Give
its 2d use. Its 3d. Its 4th. 653. What is said in reference to the
distribution of the oily matter along the edges of the eyelids? In the
ears? 654. Of what use are the perspiratory glands? How long did
Sanctorius daily weigh his food, to ascertain the amount of secretion
that passed through the skin?

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655. The average amount of perspiration is about thirty ounces; and it
passes off in such minute portions, and mixes so rapidly with the
surrounding air, that it is not perceived. For this reason, it is
called _insensible_ perspiration. When this excretion is increased, it
forms into drops, and is called _sensible_ perspiration. The following
experiments prove the existence of this excretion from the skin.

_Experiments._ 1st. Take a cold bell-glass, or any glass vessel large
enough to admit the hand, and introduce it perfectly dry; at the same
time close the mouth by winding a napkin about the wrist; in a short
time, the insensible perspiration from the hand, will be seen
deposited on the inside of the glass. At first, the deposit is in the
form of mist; but, if the experiment be continued a sufficient time,
it will collect in drops.

2d. Hold the apparently dry hand near a looking-glass, and the
invisible vapor will soon be condensed, and cover the glass with a
slight dew.

656. It is important that this excretion be maintained with steadiness
and regularity. When the action of the perspiratory glands is
suppressed, all the vessels of the different organs will suffer
mate