RECENT RESEARCHES INTO THE HISTORY OF BACTERIA. 277 



(59° C.) apply only to Bacteria hi a clear ivatery fluid. On 

 the other hand, Horwarth has studied the minimum mortal 

 temperature, and finds that Bacteria can survive after having 

 been exposed to a temperature of — 18° C; at such a point, 

 indeed, they pass into cold rigor, but at a higher tempera- 

 ture again become vitally active. The breeding and feeding 

 solution used was that which Cohn has already described ; 

 but, as in the previous account in this Journal, the propor- 

 tions of the constituents were not given, it may be well now 

 to add them : 



If kept at 50° C, this solution will remain quite free from 

 Bacteria. 



From eighteen experiments carried out for the purpose of 

 seeing the effects of different temperatures, Eidam concludes 

 that at 5° C. there is no reproduction (here it should be re- 

 marked, that a similar tube to those which produced this 

 result was placed in a warm chamber at 30° to 35° C, and that 

 Bacteria were actively reproduced in it) ; but at 5^° C. repro- 

 duction began, though very slowly, and so on up to 10° C. ; 

 above which point reproduction began to be much more ener- 

 getic, and so continued up to 30° to 35° C. ; above 35° C. it 

 fell, at 40° the Bacteria fell into heat-rigor, and died at 60°." 



From these experiments also could be drawn a confirmation 

 of what Cohn in his first paper so wisely remarked, '' Pu- 

 trefaction is a correlate phsenomenon, not of death, but of 

 life ;"^ for in those tubes, to which the drop containing Bac- 

 teria was added, without an increase of these organisms 

 becoming apparent — that is, in those kept at very low tem- 

 peratures — there was no putrefaction, but as the temperature 

 was raised, and the Bacteria began to multiply, this concomi- 

 tant of Bacterian vitality began to show itself, and with 

 these conditions the intensity of the smell of putrefaction 

 went hand in hand. 



But there was a smell, as of cheese, in some tubes kept at 

 44° to 46°, to which albumen or peas had been added ; 

 whence came this so sure, even if so disagreeable sign of 

 vitality, if it be true that at such temperatures Bacterium 

 termo is in a state of heat-rigor ? Microscopical examination 

 revealed the presence of Bacillus-filaments and lasting spores ; 



' Heft II, p. 204. 



