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abscess on the ball of the finger produced by jagging it with
a broach. It was a pretty sore finger. I don't know how it
is this morning. He had planted micro-organisms of patho-
genic qualities with that broach very much the same as I
am planting them in this broth with the platinum needle, and
they produced their results there. (Tube No. 5 was planted.)
Now, here are two tubes that I will keep with the others
without planting, place them in the incubator as controls.
That will, perhaps, be enough to illustrate the results. It is
exceedingly rare that I plant a tube of broth in that way and
fail to get a growth ; it will not occur once in a hundred
times if the broth is in condition for micro-organisms to
grow.

Physiology of Micro=Organisms.

In order that we may understand how micro-organisms
produce disease, it seems necessary that we enter into some
study of the physiological processes of plants, for micro-or-
ganisms do not produce disease by any physical power they
exert, but through their power of changing the chemical qual-
ities of the material in which they grow and the production
of poisons by these processes. We may have colonies of
non-pathogenic microbes growing and not be much the
yorse for it. The mere physical presence of these very
minute bodies does not seem necessarily to produce irritation.
It is only from those microbes that when growing produce
poisons that are instilled into the blood or into the tissues
that we get disease from micro-organisms. Then the physi-
ological processes by which these are produced become very
important to us. Life is continued through its power of
inducing chemical changes in matter. In order that life may
continue to exist these chemical changes in matter must be
continually going on and be under the control of the life
force. Whenever life fails to keep up a continued series of
chemical changes in matter, life ceases to exist—death re-
sults. It is therefore important for us to know something
about how these changes are produced or follow them up as
closely as may be and get the general idea, at least, of these
changes. There are some conditions under which life may
continue to exist in a dormant state without these chemical
changes going on, as in the seed or in the egg, or in some

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