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34                   PATHOGENIC BACTERIA.

want of food and because of the presence of other con-
ditions unfavorable to their existence."

When the conditions for rapid multiplication are no
longer good, the organism assumes a protective attitude
and develops in its interior small oval eggs, seeds, or, as
the}' are more correctly called, spores (Fig. i). Such

a                                1)                            c                       d                    e                          f

<r.—:§)        o        o o

FIG. i.—Diagram illustrating sporulation : a, bacillus enclosing a small oval
spore; £, drumstick bacillus, with the spore at the end; c, clostridium; d9 free
spores; e and ft bacilli escaping from spores.

spores developed within the bacteria are called endospores.
When the formation of such a spore is about to com-
mence, a small bright point appears in the protoplasm,
and increases in size until its diameter is nearly or quite
as great as that of the bacterium. As it nears perfection
a dark, highly-refracting capsule is formed about it. As
soon as the spore arrives at perfection the bacterium
.seems to die, as if its vitality were exhausted in the
development of the permanent form.

JEndospores are generally formed in the elongate bac-
teria—bacillus  and spirillum—but  Zopf has  described
similar bodies  as  occurring  in  micrococci.    Escherich'
also claims to have found undoubted spores  in a form
of sarcina.

The spores found in the bacilli are either round or
oval. As a rule, each bacillus produces a single spore,
which is situated either at its centre or at its end. When,
as sometimes happens, the diameter of the spore is greater
than the diameter of the bacillus, it causes a bulging of
the organism, with a peculiar appearance described as
clostridium. When the distending spore is in the centre
of the bacillus, it produces a barrel-shaped organism;
when situated at the end, a '(Trommelschlager,'J or drum-
stick-shaped one. As the degeneration of the protoplasm
of the bacillus sets the spore free, it appears as a clear,