The rapidity of their
multiplication may be accelerated, or they may be compelled to lie
dormant and inactive for a time; and, on the other hand, by exhausting
the constituents of the soil upon which they depend for life, they may
be killed.
It is a most curious fact, also, that it is possible by selecting and
cultivating only the lighter colored specimens of a certain purple
bacterium for the bacteriologist to obtain finally a plant which is
nearly white, but which has the essential characteristics of the
original purple fungus. In this we see the same power which the
florist has to alter the color of the petals of his flowers by various
methods of selective breeding.
The destruction of bacteria by means of heat and antiseptics is the
essence of modern surgery. It is, then, by preventing access of these
parasitic plants to the human organism (aseptic surgery), or the
destruction of them by chemical agents and heat (antiseptic surgery),
that we are enabled to invade by operative attack regions of the body
which a few years ago were sacred.
When the disease-producing bacteria gain access to the tissues and
blood of human and other animals by means of wounds, or through an
inflamed pulmonary or alimentary mucous membrane, they produce
pathological effects, provided there is not sufficient resistance and
health power in the animal's tissues to antagonize successfully the
deleterious influence of the invading parasitic fungus.
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