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41
that where persons are most predisposed to
Diarrhoea, there they are most liable to be attacked
with Cholera.
General Theory of Zymotic Disease.
The nature of contagious diseases and the laws of
their propagation are very little understood by the
population generally, and that is why they frequently
pursue an unrestrained course, both in our country
and town populations. A Zymotic Disease is one
that is produced by some special or general poison,
the germs of which being introduced into the blood
are capable of so altering the qualities or character
of the blood as to cause disease or death in the
system. In order, however, for these poison germs
to act, there are two other conditions necessary,
and these are that the person acted on should be
predisposed to take the poison, and that there
should be a medium of transit for the poison to
the person infected.
1. The Poison. The poisons of Zymotic disease
are of two kinds, special and general. The special
poisons are those which produce specific diseases.
Thus the poisons of Scarlet Fever, Small Pox,
Typhus Fever, and Cholera, are special poisons,
and when introduced into the system will produce
no other diseases, but that of the body from which
they come. They are like the seeds of plants
which only produce the kind of plant from which
they come. Under the microscope, these poisons
present themselves under the form of minute cells