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like a grape bunch, and hence the term staphylococcus, which ;
in the Greek means a bunch of round forms, as a grape
bunch.
(Changing slides, Fig. 9.) This you will recognize at
once as an entirely different growth form. These are what
we call bacilli, and they divide upon one pole, just
the same as the coccus forms. Now we may have coccus
forms that are like biscuits laid together upon their
flat sides. We may have coccus forms that are inclined
to be elongated. We may have rod forms, that are very
short, so that the coccus forms and the bacilli forms run
imperceptibly into each other. Some of those you will
find are a little curved generally they are straight.
;
All of these I have obtained from the human mouth, but
the human mouth is not the general habitat of this micro-
organism. It is the bacillus liquefaciens. It liquefies gelatin
readily, but is a saprophyte.
(Changing slides, Fig. 10.) Here is another, and while
these rods seem to be very much like the previous ones, it
is entirely a different species of micro-organism. It has dif-
ferent habits ; it has different forms of growth upon agar
agar and gelatin ; it has a different form of spore formation.
Here (pointing out) we see this club end enlargement and in
it a spore is formed. Here is one just beginning to enlarge
here is an escaped spore, for after the spore forms the
cell goes to pieces. This is one of the common saprophytes.
(Changing slides. Fig. 11.) This is a bacillus that we
find in the human mouth constantly—bacillus albus. We find
it in every mouth. It is a bacillus that is continually asso-
ciated with the saliva. It forms acid very readily, and I see
o:^
no reason why it should not be a caries fungus ; and yet I
very seldom see it in the deep layers of carious dentin. Dr.
Miller and others seem to have found it in the deep layers
of carious dentin frequently.
(Changing slides.) Here is another specimen of the
same micro-organism. You will see it is in short rods.
(Changing slides. Fig. 12.) Here is a different species
again—the bacillus butyricus—in which the ends of the rods
are all round or inclined to be sharp. These enlarge into
o^ boat shapes and a spore forms in the center of the cell. Here
is one with spore formation, and there are several others.

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