nd has recently been communicated to me by several
reliable witnesses, in which the flame was extinguished by closing the
mouth and nose, thus excluding the pure air that supported the
combustion, until the unfortunate experimenter could remove the candle
by which his breath had taken fire. This illustration will explain how
the odor of different substances is frequently perceptible in the breath
long after the mouth is free from them.

The lungs not only exhale waste matter, but _absorption_ takes place
from their lining membrane. In both of these respects there is a
striking analogy between the functions performed by the lungs and the
skin. When a person breathes an atmosphere loaded with the fumes of
spirits, tobacco, turpentine, or of any other volatile substance, a
portion of the fumes is taken up by the absorbing vessels of the lungs,
and carried into the system, and there produces precisely the same
effects as if introduced into the stomach. Dogs, for example, have been
killed by being made to inhale the fumes of prussic acid for a few
minutes. The lungs thus become a ready inlet to contagion, miasmata, and
other poisonous influences diffused through the air we breathe.

From this general explanation of the structure and uses of the lungs, it
is obvious that several conditions which it is our interest to know and
observe are essential to the healthy performance of the important
function of respiration. The first among these is a healthy original
formation of the lungs. No fact in medicine is better established, says
Dr. Combe, than that which proves the hereditary transmission, from
parents to children, of a constitutional liability to pulmonary disease,
and especially to consumption; yet, continues he, no condition is less
attended to in forming matrimonial engagements.

Another requisite to the well-being of the lungs, and to the free and
salutary exercise of respiration, is a due supply of rich and healthy
blood. When, from defective food or impaired digestion, the blood is
impoverished in quality, and rendered unfit for adequate nutrition, the
lungs speedily suffer, and that often to a fatal extent. The free and
easy expansion of the chest is also indispensable to the full play and
dilation of the lungs. Whatever interferes with or impedes it, either in
dress or in position, is obviously prejudicial to health. On the other
hand, whatever favors the free expansion of the chest equally promotes
the healthy ac