long-prescribed antiseptic agents; even when
considerably diluted, still powerful. He adds
the following substances to his list. Alkalies
and salts; gum-resins, such as myrrh-assafœtida,
aloes, and terra japonica; decoctions
of Virginian snake-root, pepper, ginger,
saffron, sage, mint, contrayerva root, valerian,
rhubarb, angelica, senna, common wormwood;
and to some extent, mustard, celery,
carrots, turnips, garlic, onions, cabbage,
colewort, and horseradish. Lime, he says,
prevents, but does not remove putrefaction;
while astringent mineral acids, and ardent
spirits, "not only absorb the matter from the
putrescent substance, but likewise crisp up
its fibres, and thereby render it so hard and
durable, that no change of combination will
take place for many years." Molasses closes
this list of Dr. Macbride, drawn out in the
latter half of the eighteenth century. In
seventeen hundred and seventy-three, Guyton
Morveau proposed fumigating hospitals with
muriatic acid vapours; and in seventeen
hundred and eighty, Dr. Carmichael Smyth
used nitrous fumes at Winchester, and in the
Fleet, without giving the French chymist the
credit of that rediscovery of antique wisdom,
—namely, acid fumigation. Parliament, in
eighteen hundred and two, voted five thousand
pounds to Dr. Smyth; and poor Guyton
Morveau was horribly disgusted, both at
the theft and its unjust reward. As well he
might be. In seventeen hundred and seventy-one
and seventeen hundred and seventy-two,
Fourcroy discovered the properties of chlorine
as a fumigating agent; and Dr. Cruikshank
introduced the application of it to us in
England. "All these acids," says Dr. Angus
Smith, "are very violent, and fitted only for
extreme cases, which ought not to be allowed
to occur. Chlorine may be excepted; it may
be used with advantage in minute quantities,
at least for a limited period. When applied to
centres of putridity, the great objection to it
is, that it destroys the ammonia, sending
off the nitrogen as a not very pure gas.
It soon acquires much moisture, loses its
power, and gives a very unpleasant odour to
the hand when touched. Its destruction of
manures is, however, the principal objection
to it."

"Chlorine acts by uniting with hydrogen,
acids by uniting with the compounds of
hydrogen—water and ammonia. Chlorine
decomposes the sulphur and phosphorous
compounds of hydrogen. It will even dissolve
a piece of flesh, so as to form a transparent
liquid."

Oxygen has a double action: the first is to
cause putrefaction, the second oxidation or
disinfection. In soldering preserved meats
in air-tight vessels, not a trace of air must be
left behind; and one bubble of oxygen in
grape-juice ready to ferment, will originate
that process through the whole quantity.
Hildenbrand found that meat in a vessel of
oxygen, putrified in eleven hours. Sweeny
preserved meat in water by first boiling out
the air, cooling it, covering it with a stratum
of oil to keep out the air, and adding iron
filings to absorb what might have been
allowed to enter. Meat preserved thus
remained sweet for seven months. Leuch added
a covering of oil also, but used unboiled
water and sulphur, instead of iron. His
process kept the meat sweet for only two
months. The Damaras of South Africa cut
their meat into strips, and dry it in the sun;
for simple dryness arrests decay and prevents
infection. So does intense cold. As for the
first method, Dr. Henry disinfected the
clothes of fever patients by baking them.
But to return to our oxygen.

"Air being the initial cause of putrefaction,"
we are quoting Dr. Smith, "it would
seem strange to class it among disinfectants,
but in some respects it is the greatest of all.
Its first action is mechanical, as in natural
or artificial ventilation. It is known that
the worst plagues have arisen in great calms;
crowded rooms and unchanged air increase
almost every disease, whilst ventilation has
a contrary effect. The action of the air on
putrid matter is too slow for many of the
wants of civilisation, and hence the need of
an artificial disinfectant. But, Nature
herself has a mode of hastening it by giving an
increased power to it under the influence of
porous bodies. The porous body most in use
is the soil, which is a powerful disinfecting
agent: so much so that putrid matter, when
completely absorbed by it, unless in excessive
quantities, entirely loses its smell, and
water drained from the soil at a sufficient
depth is found to have lost all its organic
matter; so thoroughly has it been disinfected.
In doing this, oxygen is absorbed; and it
will be found that water containing
decomposing organic matter, has its oxygen
removed, serving frequently as a useful index
to the state of the decompositions going
forward."

The soil, by virtue of its porosity, presses
gases into smaller space than they occupy
under ordinary atmospheric pressure, and
thus mechanically compels combination. But
for this power, the soil of towns would be
one mass of corruption; whereas, the water
from the soil of towns is much valued,
even when too impure for drinking. "This
is caused by the formation of nitric acid,
which is the result of purification, and not
only so, but a reservoir of air or oxygen,
wherewith to purify still more."  This
purifying power of percolation is the reason why
the Thames  "is not intolerable;"  were it not
for this, that river would indeed be the great
River of Death to London. The reason, also,
why charcoal is so valuable as a disinfecting
agent, is, that being one of the most porous
bodies, it absorbs impure gases and oxidises
them.  But, it does not preserve organic
substances. Mr. Condy lias applied condensed
oxygen as a disinfecting agent, and French