The very curious fact, that fixed air not only preserves bodies from
becoming septic, but is also possessed of the power of restoring
sweetness to them when actually putrid, seemed to be established by a
number of very accurate experiments adduced in support of the doctrine
by its ingenious author. This has, however, lately been controverted
by a learned writer, who has favoured the public with _an Experimental
Inquiry concerning the causes which have been generally said to produce
putrid diseases_, in which he has recounted several experiments, in
direct contradiction to those of Dr. Macbride. The authorities of both
these gentlemen deserve considerable attention, and it might seem
presumption in me to attempt to decide between them, had I only my own
opinion to adduce; but as the accuracy of the following trials was
witnessed by a Physician, well known for his medical and philosophical
writings, I feel the less diffidence in submitting them to the public.
They were made with a view, only, to my own information, having in one
of the former chapters recommended Magnesia to be taken in the act of
effervescence with an acid, as a corrector and evacuant of putrid bile;
but as the event appeared to be so satisfactory, and as a determination
of this point is the more important, from the late introduction of
fixed air as an article of the materia medica, I hope I shall not be
deemed to have impertinently obtruded into the dispute by relating
them, and endeavouring to point out what, probably, has been the cause
of Dr. Alexander's drawing conclusions, so contrary to those of the
other celebrated experimentalist.
In the experiments which Dr. Alexander has related in support of his
opinion, he has made use of the following methods. He included pieces
of putrid mutton in bladders, one containing _four ounces in measure_
of fixed air from fermenting wort; another the same quantity from wort
with a piece of putrid mutton in it; and the third, only _about half
the quantity_ from a mixture of bread, water, and saliva. In another
experiment, he exposed a slice of beef that had just begun to have the
putrid smell, to a stream of air brought over from an effervescing
mixture of distilled vinegar and salt of wormwood. In a third, the
putrid flesh was suspended in the neck of a wide mouthed bottle,
while _four ounces_ of distilled vinegar were made into _spirit.
minderer._ In a fourth, _four ounces_ of air from bottled small beer
were confined twenty-four hours with the putrid substance, which in
a fifth experiment was put into the neck of a bottle of small beer,
while it fermented before the fire for half an hour. In a sixth, the
septic body was included in a bottle with _eight ounces_ of air from
an effervescing mixture of common vinegar and salt of hartshorn. In
one only, out of all these experiments, he found the beef in any-wise
sweetened, and even in that single instance, though he at first thought
the piece a little changed, yet when washed it recovered its putrid
smell. However he confesses, that by bringing over fixed air from
several other fermenting and effervescing mixtures, on pieces of meat
just beginning to putrefy, they were rendered a little sweeter, though
never to such a degree, as entirely to lose their putrid taint.
So very different an account of so interesting a subject was truly
mortifying: The old adage, _experientia fallax, judicium difficile_,
seemed to be too applicable to the present occasion. Some cases, in
which fixed air used medicinally as an antiseptic, appeared to have
produced good effects, had occurred to some of my medical friends[v],
and I even flattered myself that I had directed it to good purpose
in an instance or two. But if the theory on which this practice was
founded should be false, the whole superstructure seemed likely to be
destroyed. On revising Dr. Alexander's book, I imagined that I had
discovered some thing in the conducting of his experiments, which might
account for their terminating so differently from those of Dr. Macbride.
[v] See Dr. Percival's Experiments and Observations, p. 72; Dr.
Priestley's papers on factitious air; and Mr. White's Treatise on the
Management of Pregnant and Lying-in Women, p. 203.
The largest quantity of fixed air which Dr. Alexander made use of
in any of these experiments was _eight ounces in measure_, and in
one instance, only two ounces were employed to sweeten the putrid
substance. In that where the meat was suspended in a wide mouthed
bottle while the vinegar was made into _spirit. minderer._ no method
seems to have been taken to retard the too rapid flight of the fixed
air, which, from the quick distribution of the salt, would be soon
dissipated. From hence I suspected, that a larger atmosphere, or a
longer continued stream of fixed air might be requisite to restore
septic bodies to perfect sweetness; and in order to decide this point,
the following experiments were instituted, having previously obtained
some slices of beef so exceedingly putrefied as to render the foetor
of them scarcely tolerable.