STUDIES ON FERMENTATION. 



301 



On June 28th, fermentation was quite finished ; there was 

 no longer any trace of gas, nor any lactate in solution. All 

 the infusoria were lying motionless at the bottom of the flask- 

 The liquid clarified by degrees, and in the course of a few days 

 became quite bright. Here we may inquire, were these 

 motionless infusoria, which from complete exhaustion of the 

 lactate, the source of the carbonaceous part of their food, were 

 now lying inert at the bottom of the fermenting vessel — were 

 they dead beyond power of revival ? * The following experi- 

 ment leads us to believe that they were not perfectly lifeless, 

 and that they behave in the same manner as the yeast of beer, 

 which, after it has decomposed all the sugar in a fermentable 

 liquid, is ready to revive and multiply in a fresh saccharine 

 medium. On April 22nd, 1875, we left in the oven, at a 

 temperature of 25° C. (77° F.), a fermentation of lactate of 

 lime that had been completed. The delivery tube of the flask, 



Fig. 73. 



The carbonaceous supply, as we remarked, had failed them, and to 

 tliis failure tlie absence of vital action, nutrition, and multiplication was 

 attributable. The Liquid, however, contained butp'ate of lime, a salt 

 possessing properties similar to those of the lactate. Why could not 

 this salt equally well support the life of the vibrios ? The explanation of 

 the difficulty seems to us to lie simply in the fact that lactic acid produces 

 heat by its decomposition, whilst butyric acid does not, and the vibrios 

 seem to require heat during the chemical process of their nutrition. 



