Individuals differ greatly in the quantity of the supply of the juices
of the mouth which are active in salivation. They differ so much that
it is safe to say that no two have equal provision.
One person may dispose of a morsel of bread in thirty mastications so
that the last vestige of it has disappeared by involuntary process into
the stomach. Another person, of similar general health appearance,
selecting as nearly as possible an equal morsel of bread, may require
fifty acts of mastication before the morsel has disappeared. The
next week, by some change of conditions this order may be reversed.
While there may be some structural or chemical difference in the two
morsels of bread, this is not sufficient to account for the different
mastications required. The dissimilarity lies in the difference of the
copiousness and strength of the secretions at the time of trial.
This liability to changed conditions would constitute a serious
danger if it were not for the protective Food Filter, or, Reflex of
Deglutition, which Van Someren has so well described in the "A.B.-Z;"
and whenever mouth-treatment of anything to be ingested is neglected,
and forced swallowing--hasty bolting of food or gulping of liquid
food--is indulged in, this protection is eluded and the danger is
converted into actual internal self-abuse.