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36                   PA THOGENIC BA CTERIA.

of these is much less clear. It seems to be an effort to
convert the entire microbe into a permanent form. This
process is observed particularly in the micrococci, where
the substance of a cell is said to break up into segments,
each of which becomes a resisting body fruitful in prop-
agating its species. Of the arthrospores little has, so
far, been learned. It is not improbable that among the
micrococci, and also among some of the smaller bacilli
in whom no spores have been observed, the maintenance
of the species when conditions of life become unfavor-
able is due to the assumption of a permanent form by
some of the individuals, without the formation of any
spore-like bodies. This is at present largely a matter of
conjecture, but the indications pointing in that direction
are numerous.

It is believed by Frankel and others that sporulation
in the bacteria is not a sign of the exhaustion of nutri-
tion, but a sign of the vital perfection of the organism.
These observers regard spore-formation as analogous to
the flowering of higher plants, which takes place only
when the conditions and development are best.

Morphology.—The morphology of the bacteria is quite
varied. Three principal forms, however, exist, from which
the others seem to be but variations.

The most simple appear as minute spheres, and from

^.^      la               /^»/Tk.


^      _

FIG. 2.—Diagram illustrating the morphology of the cocci: a, coccus or
micrococcus; £, diplococcns; <r, d, streptococci; e, f, telragenococci or meris-
mopedia; g, %, modes of division of cocci; z, sarcina; /, coccus with flagella;
k^ staphylococci.

their fancied resemblance to little berries are called cocci
or micrococci (Pig. 2, a\    When the bacteria of this form