[42] The Bacteria and Vibriones with which Professor Wyman experimented were derived from different sources; and so far as I also have been able to ascertain, the Bacteria of different fluids are similarly affected by exposure to similar degrees of heat. Thus, if on the same slip, though under different covering glasses, specimens of a hay infusion, turbid with Bacteria, are mounted, (a) without being heated, (b) after the fluid has been raised to 122° F. for ten minutes, and (c) after the fluid has been heated to 140° F. for ten minutes, it will be found that, in the course of a few days, the Bacteria under a and b have notably increased in quantity, whilst those under c do not become more numerous, however long the slide is kept. Facts of the same kind are observable if a turnip infusion, containing living Bacteria, is experimented with; and the phenomena are in no way different if a solution of ammonic tartrate and sodic phosphate (containing Bacteria) be employed instead of one of these vegetable infusions. The multiplication of the Bacteria beneath the covering-glass, when it occurs, is soon rendered obvious, even to the naked eye, by the increasing cloudiness of the film.
[43] ‘Compt. Rend.,’ t. lxi. p. 1060.
[44] When boiled solutions, containing mannite, with a little nitrate and phosphate of ammonia, were employed, they always remained sterile. Similar negative results followed the employment of ox-gall. Of three decoctions of beef with which M. Meunier experimented, the two stronger of them were found to contain swarms of Bacteria in about twelve days. Of three other flasks containing boiled urine, two also proved fertile.
[45] I have employed flasks of about 1 1/2 oz. in capacity, provided with necks two feet in length. In each case, after the flask has been half filled with the fluid, the neck has been bent eight times at an acute angle.
[46] These are the only experiments which I have performed with the very long plugs of cotton-wool, though in other previous trials with plugs about 1 1/2 in. long, I have several times obtained positive results.
[47] When infusions have been employed, these have all been made as strong as possible, and have been filtered before use. Warm water has been added in quantity just sufficient to cover the substance to be infused (cut into very small pieces), and the mixture has then been kept at a temperature of from 110°–130° F. for three or four hours.
[48] Flask still in my possession, unopened.
[49] Flask still in my possession, unopened.
[50] The vapour had lost all odour of turnip. Some of the fluid which splashed over was found to be still slightly acid.
[51] This experiment is very interesting in two or three respects. A neck of half the usual length—with only four bendings—sufficed to preserve the fluid for several days; and when this fluid (which had been in the bent-neck apparatus for nine days) was sealed up in the same flask during ebullition, it remained in vacuo for thirteen days without undergoing any apparent change, and then only became turbid under the influence of a higher temperature. Yet some of the same fluid, in a flask which was hermetically sealed during the first ebullition (No. XV.) behaved as such an infusion usually does, and became quite turbid in forty-eight hours.