[32] In the proportion of ten grains of neutral ammonic tartrate, with three grains of neutral sodic phosphate, to an ounce of distilled water.
[33] It was necessary to boil the solution first, in order to destroy any living things or dead ferments which it might contain. It must contain one or the other, because an unboiled solution of this kind, in a corked bottle about half full, will always become turbid; whilst, after it has been boiled, it may be kept indefinitely under similar conditions without becoming turbid.
[34] The proportion was one drop of the fluid, opaque with organisms, to an ounce of the clear solution.
[35] Into which a piece of glass tube had been slipped to prevent collapse.
[36] Allowing even five minutes for the temperature of the 1 oz. of fluid to become equal to that of the bath, it would then have remained exposed to this amount of heat for about ten minutes.
[37] Fluids which had remained sterile would always, in the course of thirty-six or forty-eight hours after inoculation with living Bacteria, become more or less turbid.
[38] There is, however, another point of extreme interest in connection with these experiments, bearing upon the supposed universal distribution of “germs” of Bacteria and other organisms, which I will now mention. One of the flasks, which had been exposed to 140° F., and which had been hermetically sealed at this temperature, had its neck cracked (accidentally) about half an hour afterwards. Thinking it would be as well, notwithstanding this, to keep it and observe the result, its bulb was immersed in the same water-bath with the other flasks which had been prepared at the same time. Whilst the fluid in one of these which had been exposed to a heat of 131° F., became turbid in the course of a few days, this, which had been exposed to a heat of 140° F. and whose neck was also extensively cracked, remained quite clear for seven days, although to such an extent exposed to the access of germs. Its eminent suitability for nourishing the germs of such organisms was also shown, because, on the seventh day, the fluid being still clear, the blade of a penknife was dipped into it, after having been previously immersed in a solution containing living Bacteria and Torulæ, and in thirty-six hours after this inoculation, the fluid had become turbid, owing to the presence of myriads of these organisms. So that even where obvious cracks occur, and the vacuum is altogether impaired by the consequent inrush of air, such air does not necessarily carry with it germs of Bacteria—which have been supposed to be universally diffused, and capable of passing through cracks so minute as to be invisible. These results, important as they are, have not at all surprised me, because one may frequently find a previously boiled solution of the kind under consideration, remaining free from turbidity for two weeks or more, although the neck of the flask has been merely covered by a loose paper-cap (see p. [30]).
[39] ‘Nouvelles Expériences,’ etc., 1864, p. 38.
[40] ‘American Journal of Science and Arts,’ Oct. 1867.
[41] During nearly the whole of the time the temperature was kept at 113° F. It only rose to the higher temperature for about ten minutes.