necessary to administer laxative medicines.

The inner or mucous coat of the stomach and bowels is generally regarded
by physiologists as a continuation of the skin. They greatly resemble
each other in structure, and they are well known to sympathize with each
other. Eruptions of the skin are very generally the result of disorders
of the digestive organs. On the other hand, bowel complaints are
frequently produced by a chill on the surface. The mucous coat and the
skin are both charged with the double function of _excretion_ and
_absorption_. By the exercise of the _former_ function, much of the
waste matter of the system, requiring to be removed, is thrown into the
intestines, and, mingling with the indigestible portion of the food,
forms the common excrement; while by the exercise of the _latter_
function the nutritive portion of their contents is taken up, and, as we
have seen, passes into the general circulation, and contributes either
to promote growth or to repair waste.

4. EVACUATION.--This is the fourth and last principal step in the
process of digestion. After the chyle is separated from the chyme and
passes into the circulation, the indigestible and refuse portion of the
food, which is incapable of nourishing the system, passes off through
the intestinal canal. In its course its bulk is considerably increased
by the excretion of waste matter which has served its purposes in the
system, and which, mingling with the innutritious and refuse part of the
food, is thrown out of the body in the form of excrement. If the
contents of the bowels are too long retained, uneasiness is produced.
Hurtful matter, also, which should pass off by evacuation, is
reabsorbed, passes again into the general circulation, and is ultimately
thrown out of the system either by the lungs or through the pores of the
skin.

This part of the process of digestion is _very important_, for it is
impossible to enjoy good health while this function is imperfectly
performed. To secure full and natural action in the intestinal canal,
several principal conditions are necessary. These are, first,
well-digested chyme and chyle; second, a due quantity and quality of
secretions from the mucous or lining membrane of the bowels; third, a
free and full contractile power of the muscular coat, and the
unrestrained action of the abdominal and respiratory muscles; and,
finally, a due nervous sensibility to receive impressions and
communicate the necessary