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134 PATHOLOGY OF THE HARD TISSUES OF THE TEETH.
Some seem to be of the opinion that much of the make-up of
the saliva is a transudation from the blood, of constituents that
it may happen to contain at the time, together with some con-
stituents that are characteristic of this fluid. It seems to be on
this idea that Dr. Michaels bases the proposition that in the
saliva an index is to be found of the general and special bodily
conditions, when one has learned to read them. For the present
I must conclude that the finer pathological reading of the indi-
cations given by this fluid are in a chaotic state ; that only a few
things are assuming definiteness and that much time will yet be
necessary to unravel its complexities.

ACIDITY OF THE SALIVA.
The question of the reaction of the saliva has been under
especial discussion for a century, and still men are differing so
widely as to their findings that quotations would lead to confu-
sion. My own conclusion, after many examinations, is that the
saliva as it comes from the glands is very nearly neutral, but
varies within a rather narrow range from alkaline to acid. On
account of the acidity of the mucus, the mixed fluid is generally
slightly acid. This becomes more decisively acid by the fermen-
tation processes of the microorganisms that are continuously
growing in the secretions in the mouth. Some of the elements of
the saliva seem to be fermentable, and sugars and starches taken
into the mouth quickly become fermentable. If examined in the
early morning at the time of rising from bed, the saliva will, as
the general rule, redden litmus sharply. If examined after break-
fast, the acidity is much reduced. The acidity will then increase
until the next meal time, after which it will be reduced again.
This is being continually repeated. When the flow of saliva is
least, as in sleep, its acidity is increased by the fermentative
processes of the microorganisms growing in it. At meal time
fresh saliva is secreted in larger quantities, and this, with the
food, carries the superacidulated saliva away, replacing it with
that which is normal. The degree of acidity may depend in some
part upon the differences in the saliva as it comes from the
glands. But, from my own examinations, the evidence seems to
point especially to differences in the fermentation going on in the
mouth. Differences in the constitution of the saliva — probably
in its salts, possibly other matters also — seem to render decom-
positions by microorganisms much more rapid in some than in
others. Again, the complexities of the saprophitic organisms in