Page 65 - My FlipBook

NUTRIENT MEDIA FOR BACTERIA IN THE ORAL CA VITY. 39
their researches, all the glands of the oral cavity of horses, cattle,
sheep, pigs, and dogs contain a ferment which converts starch-
paste into sugar and dextrine, while "soluble modifications of
starch appear as intermediate stages. The saliva of cattle, sheep,
dogs, rabbits, etc., as well as that of horses and cows, differs
essentially from human saliva, in the strong alkaline reaction.
The inorganic ingredients (salts) contained in human saliva
are, besides chloride of potassium and chloride of sodium, com-
binations of carbonic and phosphoric acids with calcium, potas-
sium, natrium, and magnesium, calcium and natrium carbonate
preponderating (Hoppe-Seyler). Clear saliva exposed to the air
becomes cloudy through the precipitation of carbonate of lime
(Hoppe-Seyler), a fact which should be borne in mind in any
attempt to account for the formation of tartar. Human saliva
also contains slight traces of a nitrous compound, as is shown
by the appearance of a blue color upon adding saliva slightly
acidified with very dilute sulphuric acid to a dilute solution of
iodide of potassium containing starch. The presence of nitrites
in the human saliva is probably to be accounted for by a reduc-
tion of the nitrates introduced into the mouth with food and
drink.
If human saliva from an unclean mouth be acidified with
muriatic acid, and a small quantity of chloride of iron added, a
beautiful red color almost always appears, which indicates a com-
pound of sulphocyanogen. The manner in which this compound
is formed in the huroan mouth is unknown. It has been supposed
to have some connection with carious teeth, or, according to
others, with smoking ; the latter view is unquestionably erro-
neous, for I have repeatedly found the above-mentioned combi-
nation in the mouths of non-smokers.
The human saliva, as may be readily seen from the analysis,
is very poor in organic ingredients. It contains traces of an
albuminous substance which is coagulated by heat, also invaria-
bly a small quantity of mucine ; in the saliva of dogs 0.662-2.604
grams were found in 1000 (Hoppe-Seyler). Consequently, the
saliva turns slightly yellow when boiled with nitric acid, changing
to orange upon the addition of an alkali. The addition of sul-
phate of copper (CuSOi) and caustic potash (KIIO) produces