228 Prof. H. C. Bastian on the Heat [Mar. 20, 



the same slip, though under different covering-glasses, specimens of a 

 hay-infusion turbid with Bacteria are mounted, (a) without, being heated, 

 (5) 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." 



The facts just cited concerning the behaviour of thin films of turbid 

 infusions which had heen heated to different temperatures gave me the 

 clue as to the proper direction of future work. It would seem that, 

 when mounted in the manner described, such thin films of infusion 

 continue capable of supporting and favouring the multiplication of any 

 already existing Bacteria and Vibriones, although under such conditions 

 no new birth of living particles appears to take place even in these 

 fluids. The question then arose as to whether, by subjecting larger 

 quantities of the same infusions to any particular sets of conditions, we 

 could ensure that they also should continue to manifest the same 

 properties ; because if so, it would be almost as easy to determine the 

 death-point of Bacteria and Vibriones when exposed to heat in these 

 infusions, as it had been to determine it for the saline solutions already 

 mentioned. 



It was pointed out by G-ruithuisen early in the present century, that 

 many infusions, otherwise very productive, ceased to be so when they 

 were poured into a glass vessel whilst boiling, and when this was filled 

 so that the tightly fitting stopper touched the fluid. Having myself 

 proved the truth of this assertion for hay-infusion, it seemed likely that, 

 by having recourse to a method of this kind, I should be able to lower the 

 virtues of boiled hay- and turnip-infusions to the level of those possessed 

 by the boiled saline solution with which I had previously experimented 

 — that is, to reduce them to a state in which, whilst they appear (under 

 these conditions) quite unable of themselves to engender Bacteria or 

 Vibriones, they continue well capable of favouring the rapid multiplication 

 of such organisms. 



This was found to be the case; and I have accordingly performed 

 upwards of one hundred experiments with inoculated portions of these 

 two infusions raised to different temperatures. The mode in which the 

 experiments were conducted was as follows : — 



Infusions of hay and turnip of slightly different strengths were 

 employed. These infusions, having been first loosely strained through 



