On the Heat necessary to hill Bacteria &c. 459 



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 Vihriones 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 Gruithuisen 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 Hkely 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 solu- 

 tion with, which I had pre\'iously 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 Vihriones, 

 they continue well capable of favouring the rapid multiplication of 

 such organisms. 



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

 formed upwards of ene 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, ha\dng been first loosely strained 

 through musHn, were boiled for about ten or fifteen minutes, 

 and then whilst boiling strained through ordinary Swedish fntei-ing- 

 paper into a glass beaker which had previously been well rinsed 

 with boiling water. A number of glass bottles or tubes were 

 also prepared, which, together with their stoppers or corks, had 

 been boiled in ordinary tap water for a few minutes*. They were 

 taken out full of the boiling fluid ; and the stoppers or corks being 

 at once inserted, the vessels and their contents were set aside to 

 cool. When the filtered infusion of hay or turnip had been 

 rapidly cooled down to about 110° F. (by letting the beaker con- 

 taining it stand in a large basin of cold water), it was inoculated 

 with some of a turbid infusion of hay swarming with active 

 Bacteria and Vihriones — in the proportion of one drop of the turbid 

 fluid to each fluid ounce of the now clear filtered infusiont. The 

 beaker was then placed upon a sand-bath, and its contained fluid 

 (in which a thermometer was immersed) gradually raised to the 

 required temperature. The fluid was maintained at the same tem- 

 perature for five minutes by alternately raising the beaker from 



* The vessels employed have varied in capacity from two drachms to four 

 ounces ; some have been provided with glass stoppers and others with very 

 tightly fitting corks ; and the latter I find have answered quite as well as the 

 former. On the whole I have found tightly corked one-ounce phials to be about 

 the most convenient vessels to employ in these inocidation experiments. 



t It was found desirable to filter the infusions after they had been boiled, 

 because the boiling generally somewhat impaired their clearness. 



