CHAPTER I
BACTERIA.

A BACTERIUM is a minute vegetable organism consist-
ing of a single cell principally composed of an albumin-
ous substance, which Nencki has called mycoprotein.
Nencki found the chemical analysis of bacteria in the
active state to consist of 82.42 per cent, of water. In
100 parts of the dried constituents he found 84.20 parts
of mycoprotein; 6.04 of fat; 4.72 of ash; 5.04 of unde-
termined substances.

Mycoprotein, which has the composition C 52.32, H
7-55) N 14.75, is a perfectly transparent, generally ho-
mogeneous body, which probably varies somewhat ac-
cording to the species from which it is obtained, the
culture-medium in which it is grown, and the vital
products which the organism produces by its growth.
Sometimes the mycoprotein is granular, as in bacillus
megatherium ; sometimes it contains fine granules of
chlorophyl, sulphur, fat, or pigment. Each cell is sur-
rounded by a cell-wall, which in some species shows the
cellulose reaction with iodin.

When subjected to the influence of nuclear stains the
bacteria not only take the stain faintly, but in Ğuch a
manner as to show the existence of a large nucleus situ-
ated in the centre of the cell and constituting its great
bulk. The cell-wall generally is not stained, but when
it does tinge, a delicate line of unstained material can
sometimes be made out between the nucleus and the cell-
wall, showing the existence of a protoplasm.

The anilin dyes, which possess a great penetrating
power, color the organisms so intensely as to preclude
the differentiation of the cellular constituents. Under

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