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They are different in many respects from the others, and
yet the cells are very much like the bacillus albus, with the
exception that instead of having scjuare ends they have round
or pointed ends.
(Changing slides, Fig. 13.) Here is the bacillus max-
imus, the largest bacillus that we know anything about. We
find it almost continually in the mouths of those who are not
very cleanly. We will find very few specimens of it in cleanly
mouths. It seems to be easily gotten rid of. It is a bacillus
that does no particular harm that we know of. Another fea-
ture of it is that it will not grow at all in any culture media
that we have been able to devise, and we cannot obtain pure
cultures. It is confined strictly to the saliva within the
mouth. If taken out it will not grow.
(Changing slides, Fig. 14.) Here is another of those that
cannot be cultivated ; consequently we have to take it directly
from the mouth onto the slide, and we cannot get it pure.
This is the thread fungus—leptothrix buccalis. You will find
an article in the Cosmos—about two years ago—by Dr. Will-
iams, who has made some discoveries in regard to this '^M
plant. The plant grows in long, soft filaments. Lately Dr.
Williams has found that it forms exogenous spores, but they
are so minute that they cannot be seen with anything less
than a twenty-fifth-inch lens. The spore heads can be seen
very plainly here as an enlarged end. We never suspected
that those heads were a portion of the plant that was covered
with little spores all over the outside, and yet it is found
that this is the fact, that these club ends are spore heads.
Now you have an idea of how much that is magnified, how
small it must be to make such a picture as we have here,
and then think of the fact that we have to magnify it just as
much more before we can see the form of the spores.
(Changing slides.) This is a mixture of organisms taken
from a sore mouth under a plate, and it represents the organ-
isms just as we happened to take them. Here is a large
streptococcus ; here is a smaller streptococcus ; here is bacil-
lus maximus, and so on. It gives you an idea of the variety
that we will find in any one position all growing together.
(Changing slides.) Here is one I would like to tell you a
little story about. It is a stranger I met with once, and
only once. A man came to me with a fever, with a sore

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