er of smaller lobules, and the tissue appeared to be like
that of a lymphatic gland, or "kernel," the name "adenoids" (gland-like)
was given to them. Later they were termed _post-nasal growths_, from the
fact that they lay just behind the rear opening of the nostrils; and
these two names are used interchangeably. Our knowledge has spread and
broadened from this starting-point, until we now know that adenoids are
the chief, yes, almost the sole primary cause, not merely of
mouth-breathing, but of at least two-thirds of the injurious effects
which have been attributed to this habit.

Mouth-breathing is not simply a bad habit, a careless trick on the part
of the child. We have come to realize that physical bad habits, as well
as many mental and moral ones, have a definite physical cause, and that
_no child ever becomes a mouth-breather as long as he can breathe
comfortably through his nose_.

This clears the ground at once of a considerable amount of useless
lumber in the shape of advice to train the child to keep his mouth shut.
I have even known mothers who were in the habit of going around after
their helpless offspring were asleep and gently but firmly pushing up
the little jaw and pressing the lips together until some sort of an
attempt at respiration was made through the nostrils. Advertisements
still appear of sling-like apparatuses for holding the jaws closed
during sleep.

To attempt to stop mouth-breathing before providing abundant air-space
through the nostrils is not only irrational, but cruel. Of course, after
the child has once become a mouth-breather, even after the nostrils have
been made perfectly free, it will not at once abandon its habit of
months or years, and disciplinary measures of some sort may then be
needed for a time. But the hundred-times-repeated admonition, "For
heaven's sake, child, shut your mouth! Don't go around with it hanging
open like that!" unless preceded by proper treatment of the nostrils,
will have just about as much effect upon the habit as the proverbial
water on a duck's back. No use trying to close his mouth by any amount
of opening of your own.

Fortunately, as does not always happen, with our discovery of the cause
has come the knowledge of the cure; and we are able to say with
confidence that, widespread and serious as are disturbances of health
and growth associated with mouth-breathing, they can be absolutely
prevented and abolished.

What, then, is the cause of thi