CONDITIONS FATOUEING FERilENTATION. 



67 



therefore made with neutral hay-infusion and with acid turnip- 

 infusion inoculated with drops of a fluid swarming with the above- 

 named organisms. The mixture was exposed to the several degrees 

 of heat only for a period oijive minutes. In a communication to 

 the Royal Society, after classifying the results, I say* : — " The 

 experimental results above tabulated seem naturally divisible into 

 three groups. Thus, when heated only to ISl"" F., all the infu- 

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

 solution had done. 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 little below 140° F. 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 remained unaltered." The cause of 

 these discrepancies was further studied ; and in a subsequent com- 

 munication to the Eoyal Society a few months later, 1 adduced 

 evidence to show that the turbidity which had occurred after the 

 organic inoculated fluids had been subjected to a heat of 140° F. 

 (60° C.) and upwards to 158° F. (70° C.) had been due " not to 

 the survival of the living units, but rather to the fact that the 

 mere dead organic matter of the inoculating compound has acted 

 upon the more unstable organic infusions in a way which it was 

 not able to do upon the boiled saline fluids "f. The inoculating 

 compound made use of in these experiments being a fluid in full 

 fermentation, it would contain, besides organisms and their germs, 

 mere organic matter, and, as the light of subsequent investigations 

 enables me to add, possibly some soluble chemical ferments 

 produced during the vital activities of the living organisms them- 

 selves. 



These experiments were devised and carried out solely with the 

 view of throwing light upon one particular question, viz. the 

 thermal death-point of Bacteria and their germs when immersed 

 in fluids. Those of the first series also had the same reference to 

 Torulae and their germs. Having such an object before me I was 

 careful to eliminate any source of confusion which might arise 

 from the possible germinality of the mere fluids with which expe- 



* Proceedings of the Royal Society, vol. xxi, p. 231. 

 > Ibid. pp. 325-330. 



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