460 'Royal Society : — 



and replacing it upon ihe sand-bath. The bottles to be used were 

 then one by one uncorked, emptied, and refilled to the brim with 

 the heated iuoculated fluid*. The corks or stoppers were at once 

 very tightly pressed down, so as to leave no air between them and 

 the surface of the fluids. The beaker was then replaced upon the 

 sand-bath and the gas turned on more fully, in order that the ex- 

 perimental fluid might be rapidly raised to a temperature 9° F. 

 (5° C.) higher than it had been before. After five minutes' 

 exposure to this temperature other bottles were filled in the same 

 manner, and so on for the various temperatures the influence of 

 which it was desired to test. 



Thus prepared, the bottles and tubes have been exposed during 

 the day to a temperature rangiug from 65° to 75° F. And generally 

 one had not to wait long in order to ascertain what the results 

 were to be. In some cases, if the contents of the vessels were 

 to become turbid, this was more or less manifest after an in- 

 terval of forty-eight hours ; in other cases, however, the turbidity 

 manifested itself three or more days later: the reason of this 

 difference will be fully discussed in a subsequent communication. 



For the sake of simpHcity and brevity, the necessary particu- 

 lars concerning the 102 experiments have been embodied in the 

 opposite Table. 



The experimental results here tabulated seem naturally di\isible 

 into three groups. Thus, when heated only to 131° F., all the in- 

 fusions became turbid within two days, just as the inoculated saline 

 solutions had done J. Heated to 158° F. all the inoculated organic 

 infusions remained clear, as had been the case with the saline 

 solutions in my previous experiments when heated to 140° F. 

 There remains, therefore, an intermediate heat zone (ranging from 

 a httle below 140° to a little below 158° F.) after an exposure to 

 which the inoculated organic infusions are apt to become more 

 slowly turbid, although inoculated saline solutions raised to the 

 same temperatures invariably remain unaltered. The full expla- 

 nation of these apparent anomahes I propose to make the subject 

 of a future communication to the Eoyal Society ; meanwhile we 

 may quite safely conclude that Bacteria, Vihriones, and their sup- 

 posed germs are either actually killed or else completely deprived 

 of their powers of multiplication after a brief exposure to the tem- 

 perature of 158° F. (70° C). 



This evidence now in our possession as to the limits of " \'ital 

 resistance '' to heat displayed by Bacteria, Vibriones, and their sup- 

 posed germs in neutral saline solutions, and in neutral or acid or- 

 ganic infusions, is most pertinent and valuable when considered 

 in relation to that supplied by other sets of experiments bearing 

 upon the all-important problem of the Origin of Life. These 



* At this stage, of course, very great care is needed in order to avoid all 

 chance of accidental contamination either with living organisms or with un- 

 heated fragments or particles of organic matter. 



X In the experiments already referred to. 



I 



