are those substances which promote putrefaction, chiefly the calcareous earths, magnesia, and tefaceous powders. From the many curious experiments made by Sir John Pringle to ascertain the septic and antiseptic virtues of natural bodies, it appears that there are very few substances of a truly septic nature. Those commonly reputed such by authors, as the alkaline and volatile salts, he found to be no wise septic. However, he discovered some, where it seemed least likely to find any such quality; these were chalk, common salt, and tefaceous powders. He mixed twenty grains of crabs eyes, prepared with fix drums of ox's gall, and an equal quantity of water. Into another phial he put an equal quantity of gall and water, but no crabs-eyes. Both these mixtures being placed in the furnace, the putrefaction began much sooner, where the powder was, than in the other phial. On making a like experiment with chalk, its septic virtue was found to be much greater than that of the crabs-eyes: nay, what the doctor never met with before, in a mixture of two drams of flesh, with two ounces of water and thirty grains of prepared chalk, the flesh was resolved into a perfect mucus in a few days.
To try whether the tefaceous powders would also dissolve vegetable substances, the doctor mixed them with barley and water, and compared this mixture with another of barley and water alone. After a long maceration. ceration by a fire, the plain water was found to swell the barley, and turn mucilaginous and sour; but that with the powder kept the grain to its natural size, and though it fatten it, yet made no mucilage, and remained sweet.
Nothing could be more unexpected, than to find sea salt a hasterer of putrefaction; but the fact is thus; one dram of salt prelerves two drams of fresh beef in two ounces of water, above thirty hours, uncorrupted, in a heat equal to that of the human body; or, which is the same thing, this quantity of salt keeps flesh (sweet twenty hours longer than pure water; but then half a dram of salt does not preserve it above two hours longer. Twenty-five grains have little or no antiseptic virtue, and ten, fifteen, or even twenty grains, manifestly both halften and heighten the corruption. The quantity which had the most putrefying quality, was found to be about ten grains to the above proportion of flesh and water.
Some inferences have been drawn from this experiment: one is, that since salt is never taken in aliment beyond the proportion of the corrupting quantities, it would appear that it is subservient to digestion chiefly by its septic virtue, that is, by softening and revolting meats; but in making this inference, the powers of the digestive organs in modifying chemical action are not taken into account.
It is to be observed, that the above experiments were made with the salt kept for domestic uses. See Pringle's Observ. on the Dileas of the Army.