. The useless inconvertible material,
leaving every available element behind, is got rid of, either in a solid
form by the bowels, or in a fluid form by the kidneys; and thus as long
as life lasts there goes on more or less perfectly the wonderful process
of constant change, of constant renewal, and during childhood and youth,
of constant increase of size and stature.

Incomplete as this sketch is, it may yet suggest how readily one part
of this complex machinery may be thrown out of gear, and further how not
one part can suffer without all being disordered. Solid food given to
the child before it has cut its teeth, enters the stomach unreduced to
pulp by the grinders, and unmixed with the saliva, which should help its
solution, and which the undeveloped salivary glands do not yet furnish.
Too large a quantity of food, or food of an unsuitable character, on
which the gastric juice cannot act readily, may pass into a state of
fermentation; vomiting, flatulence, sour and offensive breath will be
the result, and the food will pass into the intestine unprepared to be
acted on by the bile. Exposure to cold, or the opposite condition of
excessive heat, may disturb the action of the liver, and interfere with
the secretion of bile; and the food will then pass along the intestine
in a state unsuitable for absorption. Or, again, the mesenteric glands
may be irritated by long-continued imperfect performance of the earlier
stages of digestion, or their structure may be altered, and mesenteric
disease, or consumption of the bowels, as it has been termed, may
result. From want of muscular power, or from want of care on their part
who have charge of the child, the bowels may become habitually
constipated. Health will then suffer, if the child carries about with it
for days together matters which can serve no useful purpose, but which
are to the body what an ill-kept dustbin is to the rest of the house.
Lastly, if the kidneys perform their duties imperfectly in consequence
of exposure to cold, or of the changes which some diseases, such as
scarlatina, sometimes bring about in their structure, the blood will be
imperfectly purified; dropsy and various forms of inflammation may
result; or the brain and nervous system may be disordered, and death in
convulsions may attest the dangerous nature of this blood-poisoning.

It would take too long to go in detail through all the phases of
disordered digestion in early life. Much has been already