STUDIES OX FERMENTATION. 35 



(36° F. or 54° F.) less. Wine, when fresh, ceases to be liable to 

 change after it has been brought to a temperature below 

 100° C. (212° F.) ; it requires a temperature of more than 

 100° C. in the presence of carbonate of lime. 



As regards the explanation of the influence which acidity or 

 alkalinity exerts in diminishing or increasing the tempera- 

 ture required to protect infusions and organic matters from 

 ultimate change, although this is a subject which claims special 

 study, we are inclined to believe that acidity permits, and 

 alkalinit}' prevents, the penetration of moisture into the interior 

 of the cells of the germs belonging to infusions, so that in 

 heating the outer cases of these cells in an alkaline medium we 

 heat the germs in a dry state ; and in heating the outer cases in 

 an acid medium we heat the germs when they are moist. We 

 all know that these conditions make a great difference in the 

 resistance which bodies offer to the action of heat. A particle 

 of mould which, in a moist state, cannot survive a temperature 

 of from 60° C. to 100°. C. (140° to 212° F.), will preserve its 

 fecundity even if heated to 120° C. (248° F.), if it has been 

 previously well dried.* 



The nature of the spontaneous productions which we see 

 appear in organic liquids is affected to a remarkable extent by 

 the smallest change in the compositions of those liquids. 

 Generally speaking, as we have often proved in our former 

 works, a feeble acidity is unfavourable to the development of 

 bacteria and infusoria, and, on the other hand, favourable to the 

 growth of mould. A liquid which is neutral or of feeble alka- 

 linity behaves in an exactly inverse manner. 



Those who support the theory of spontaneous generation 

 seek to find in the natural differences between the organic pro- 

 ductions of various liquids which are simultaneously exposed to 

 the same atmosphere, an argument in favour of their doctrine. 

 These differences, however, are only an effect of the greater or 

 less fitness of a peculiar liquid for a certain kind of growth. 

 When an acid organic liquid, such as the must of grapes for 



* See mv Meraoire sur les Generations dites Spontanees, already cited. 



D 2 



