FERMENTATION. 509' 



proceed from differeut fermentative agents, and that consequently diverse decom- 

 positions are produced by different bacteria. 



This much is certain, that in fermentation, as in respiration, a certain amount 

 of kinetic energy is set free by the living protoplasm and transmitted to the 

 environment, and that in this respect fermentation and respiration behave alike. 

 Thus it also becomes evident that fermentation and respiration can replace and 

 supplant one another. In many moulds, as, for example, in Mucor racernosus, 

 this substitution is very noticeable. If the mycelial threads rise up from the 

 liquid, which serves for its substratum, into the air, and if they can draw oxygen 

 from the surrounding atmosphere, then respiration takes place; but if this mould 

 is submerged in the liquid, so that it can no longer obtain free atmospheric 

 oxygen, then the cells become altered, pass into the sprout form, and instead of 

 respiration we observe in them the ferment-action described. Submersion may 

 be regarded as an abnormal condition for these moulds, and perhaps for Yeast 

 also, but for bacteria it is scarcely so, and for them respiration must be regarded 

 rather as the abnormal condition. 



I cannot close these speculations without again repeating that fermentation 

 and respiration are only carried on by living protoplasm, that the movements 

 which thus proceed from the protoplasm cease immediately life is extinguished, 

 and that these movements must be assigned to that force of nature acting in the 

 protoplasm for which I claim the old term " vital force ". 



