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formation may be the result and an abscess will occur. —
In
this way we may get abscesses occurring one after the
other—metastatic abscesses, we say, in neighboring locali-
ties. It is a question whether this micro-organism is ever re-
sponsible for the beginning of an inflammatory movement.
The inflammatory movement is begun by something else
first, then the micro-organism, by the irritation it produces
by its enzyme and by its waste products, increases the inflam-
mation very materially and melts down the inflammatory
products, causing pus formation. This subject, however,
will come up later and we will have something more to say
of it. I want to bring it to your attention frequently, be-
cause of its great importance in dental practice.
The Yeast Plant.
I want to hold your attention for a little time yet to the
subject of the physiology of micro-organisms, and to do this
we will take up the yeast plant, the agent of alcoholic fer-
mentation. It is one of the best examples of the fermenta-
tive organisms, and the one that has been best studied
one that is cultivated by all brewers—and a very large prac-

tical use is being made of it. If a few cells of this plant are
placed in sweetened water and kept at room temperature, or,
better, at a temperature of 90 to 95 degrees, it grows quite
rapidly, producing its clusters of cells, hanging together or
budding out irregularly and producing groups of cells. If
this is grown in considerable quantity and then washed in
distilled water carefully until all extraneous matter has been
removed from the yeast and then is steeped in distilled w^ater
for a time and the water filtered away, evaporated, we will
obtain a white amorphous powder, not properly a crystal-
line substance, but a powder without form. This powder
may be kept in the dried state indefinitely. If we redissolve
this and add it to a solution of cane sugar the sugar will be
digested and converted into glucose. This powder, then, is
the enzyme of the plant, the diastase, similar in every way,
apparently, to the diastase formed by the grain of corn in
its growth, and similar to the pepsin from the animal. The
yeast in its growth liberates carbonic acid gas, and alcohol
is formed as the second waste product. There are not
necessarily two waste products from every plant. Some
plants have a larger number, five or six distinct waste prod-

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