#Results of Bacterial Growth.#--Some organisms, such as those of tetanus
and erysipelas, and certain of the pyogenic bacteria, show little
tendency to pass far beyond the point at which they gain an entrance to
the body. Others, on the contrary--for example, the tubercle bacillus
and the organism of acute osteomyelitis--although frequently remaining
localised at the seat of inoculation, tend to pass to distant parts,
lodging in the capillaries of joints, bones, kidney, or lungs, and there
producing their deleterious effects.

In the human subject, multiplication in the blood-stream does not occur
to any great extent. In some general acute pyogenic infections, such as
osteomyelitis, cellulitis, etc., pure cultures of staphylococci or of
streptococci may be obtained from the blood. In pneumococcal and typhoid
infections, also, the organisms may be found in the blood.

It is by the vital changes they bring about in the parts where they
settle that micro-organisms disturb the health of the patient. In
deriving nourishment from the complex organic compounds in which they
nourish, the organisms evolve, probably by means of a ferment, certain
chemical products of unknown composition, but probably colloidal in
nature, and known as _toxins_. When these poisons are absorbed into the
general circulation they give rise to certain groups of symptoms--such
as rise of temperature, associated circulatory and respiratory
derangements, interference with the gastro-intestinal functions and also
with those of the nervous system--which go to make up the condition
known as blood-poisoning, toxæmia, or _bacterial intoxication_. In
addition to this, certain bacteria produce toxins that give rise to
definite and distinct groups of symptoms--such as the convulsions of
tetanus, or the paralyses that follow diphtheria.