1873.] necessary to kill Bacteria, Vibriones., fyc. 227 



heated to 122° or 131° F. became quite turbid iu about two days, whilst 

 those which had beeu raised to 140° F. or upwards as invariably 

 remained clear and unaltered. The turbidity in the first series having 

 been ascertained to be due to the enormous multiplication of Bacteria and 

 Vibriones, and it being a well-established fact that such organisms when 

 undoubtedly living always rapidly multiply in these fluids, the conclusion 

 seemed almost inevitable that the organisms and their germs must have 

 been killed in the flasks which were briefly subjected to the temperature 

 of 140° F. How else are we to account for the fact that these fluids 

 remained quite unaltered although living organisms were added to them 

 in the same proportion as they had been to those less-heated fluids 

 which had so rapidly become turbid ? Even if there does remain the mere 

 possibility that the organisms and their supposed germs had not actually 

 been killed, they were certainly so far damaged as to be unable to 

 manifest any vital characteristics. The heat had, at all events, deprived 

 them of their powers of growth and multiplication ; and these gone, so 

 little of what we are accustomed to call " life " could remain, that prac- 

 tically they might well be considered dead. And, as I shall subse- 

 quently show, the production of this potential death by the temperature 

 of 140° F. enables us to draw just the same conclusions from other expe- 

 riments, as if such a temperature had produced a demonstrably actual 

 death*. Seeing also that these saline solutions were inoculated with 

 a fluid in which Bacteria and Vibriones were multiplying rapidly, we 

 had a right to infer that they were multiplying in their accustomed 

 manner, " as much by the known method of fission, as by any unknown 

 and assumed method of reproduction." So that, as I at the time saidf, 

 " These experiments seem to show, therefore, that even if Bacteria do 

 multiply by means of invisible gemmules, as well as by the known 

 process of fission, such invisible particles possess no higher power of 

 resisting the destructive influence of heat than the parent Bacteria 

 themselves possess." 



This is, in fact, by far the most satisfactory kind of evidence that can 

 be produced concerning the powers of resisting heat enjoyed by Bacteria 

 and Vibriones, because it also fully meets the hypothesis as to their 

 possible multiplication by invisible gemmules possessed of a greater power 

 of resisting heat, and because no mere inspection by the microscope of 

 dead Bacteria can entitle us positively to aflirin that they are dead, 

 even though all characteristically vital or " true living" movements may 

 be absent. 



Facts of a very similar nature were mentioned hi the same work 

 strongly tending to show that Bacteria and Vibriones are also killed at 

 the same temperature in other fluids, such as infusions of hay or turnip. 

 These facts were referred to in the following statement^ ; — " Thus, if on 



* See p. 232. 



t Modes of Origin of Lowest Organisms. 1871, p. 60. J Loc, cif. p. 60. 



