of our teeth, but to retain them as long as possible.
Teeth, as we well know, are prone to decay. We may inherit poor and soft
teeth: our mode of living may make bad teeth worse. If an ounce of
prevention is ever worth a pound of cure, it is in keeping the teeth in
good order. Bad teeth and toothless gums mean imperfect chewing of the
food and, hence, impaired digestion. To attain a healthful old age, the
power of vigorous mastication must be preserved.

One of the most frequent causes of decay of the teeth is the retention of
fragments of food between and around them. The warmth and moisture of the
mouth make these matters decompose quickly. The acid thus generated
attacks the enamel of the teeth, causing decay of the dentine. Decayed
teeth are often the cause of an offensive breath and a foul stomach.

[Illustration: Fig. 64.--Lymphatics on the Inside of the Right Hand.]

To keep the teeth clean and wholesome, they should be thoroughly cleansed
at bedtime and in the morning with a soft brush and warm water. Castile
soap, and some prepared tooth-powder without grit, should be used, and the
brush should be applied on both sides of the teeth.

The enamel, once broken through, is never renewed. The tooth decays,
slowly but surely: hence we must guard against certain habits which injure
the enamel, as picking the teeth with pins and needles. We should never
crack nuts, crush hard candy, or bite off stout thread with the teeth.
Stiff tooth-brushes, gritty and cheap tooth-powders, and hot food and
drink, often injure the enamel.

To remove fragments of food which have lodged between adjacent teeth, a
quill or wooden toothpick should be used. Even better than these is the
use of surgeon's floss, or silk, which when drawn between the teeth,
effectually dislodges retained particles. If the teeth are not regularly
cleansed they become discolored, and a hard coating known as _tartar_
accumulates on them and tends to loosen them. It is said that after the
age of thirty more teeth are lost from this deposit than from all other
causes combined. In fact decay and tartar are the two great agents that
furnish work for the dentist.[26]

169. Hints about Saving Teeth. We should exercise the greatest care
in saving the teeth. The last resort of all is to lose a tooth by
extraction. The skilled dentist will save almost anything in the shape of
a tooth.

People are often urged and consent to have a number of teeth extracted
which, wi