Note 42 — THE MODES OF ORIGIN OF LOWEST ORGANISMS.

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.