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41
and consequently softer. If on the contrary it passes through a clayey
bed, it will hold in solution certain salts which are peculiar to such soil.
A river varying much in level at different times, will be generally an
unfit supply for internal use, from the occasional miasmatic nature of its
banks when but partially covered with water and exposed to the sun's rays,
as well as from the less diluted impurities which are undoubtedly mixed
with it in passing through a cultivated tract.
When there is a large body of water, on the contrary, unless there is
most extensive pollution, the impurities may be almost too diluted to be
appreciable.
But as poisons contained in water are introduced into the system in the
most subtle form, and in a condition which renders them most easily
absorbed by the fluids of the body, and in a most unobserved and gradual
manner, it behoves those who have the custody of the public health to look
well into the sources of supply; and where public companies are concerned,
to its proper and efficient filtration prior to service.
Cause IV. Adulterated Food.
This subject in its many varieties is so familiar to you from the recent
able investigation of the subject as published in the "Lancet," that entering
into details would be a work of supererogation on my part, and would
unnecessarily occupy your time.
I may, however, in impressing the importance of procuring food in a
pure state, recall to your recollection a few pernicious admixtures, viz.—
alum in bread, Prussian blue in green tea, the occasional admixture of
the excrement of the silk worm in black tea, salts of copper in pickles,
red lead and vermillion in anchovy sauce and paste, arsenic and copper in
certain green coloured sweetmeats, chicory in coffee, &c. &c.
Cause V. Animal Food rendered Poisonous from Diseased Action or Partial
Decomposition.
Dr. Christison mentions a poison contained in the blood of over-driven
cattle, noticed by Morand in the year 1776, in which the animal seemed
to vary little from its natural condition ; but in which, if any of tho^raw
meat or blood were applied to a scratch, or even sometimes to the
unbroken skin, produced severe inflammation or malignant boils.
Another disease, fortunately rare in this country, is common on the continent,
in which animals are affected with boils, a disorder called " milzbrand."
This distemper renders the animal so poisonous, that those who
handle the skin or entrails, or who eat the flesh, are apt to suffer severely.
Sometimes cholera is produced, but more commonly typhus fever, or malignant
pustules, which diseases are frequently fatal in a few hours.
The tendency of decomposition to impart deleterious qualities to animal
matter previously wholesome, has been long known.
To those unaccustomed to the use of tainted food, the mere commencement
of decay is insupportable.
Game decayed only sufficiently to please the taste of the epicure, has produced
severe cholera in persons not accustomed to eat it in that state.
Gaspard, ilajendie, Leuret, and Stamont, have proved by experiment,
that putrid animal matte*, introduced into the veins of healthy animals,
quickly proved fatal, producing a disease resembling typhus fever; and