CHANGES IN FERMENTATION. 625 



acids resist fermentation, but are to a certain extent 

 good nutrient media. 



The splitting up of the fermentescible substances never 

 forms the only physiological act of the organisms which 

 take part in it. It is evident that nutrition, growth, and 

 multiplication of the cells must go on at the same time, 

 and for this purpose the fermentescible materials do not, 

 as a rule, suffice, but salts, nitrogenous substances, and 

 at times also carbon substances, must also be at the 

 disposition of the fungi; when oxygen is excluded, the 

 presence of a particularly good nitrogenous nutrient 

 material is an absolute necessity for continued growth. 

 Further, the protoplasm, as the result of its action, must 

 always be to a certain extent used up, and thus the pro- 

 ducts of the destructive tissue change must appear, only, 

 in this case, the want of oxygen must bring about a 

 conformity of these products with those of the intra- 

 molecular respiration. It is for the progress of this 

 assimilating and destructive tissue change that the 

 necessary energy is obtained as the result of the fermen- 

 tation, although the sum of the material which is directly 

 utilised for this tissue change appears to be very small in 

 relation to the amount of fermentescible substance which 

 is broken up; according to Pasteur, the amount of the 

 sugar employed for nourishment, for example in an 

 energetic fermentation of sugar by means of yeast, 

 amounts only to 1 per cent, of the fermented mass. 



As, in this way, the fermentative processes, up to a Is the fer- 

 certain point, go on alongside of the ordinary tissue materS? ' 



change, the further question arises whether it is neces- Broken up in 



the cells r 

 sary for the occurrence of the fermentations that the 



fermentescible material, like the nutrient material, must 

 not only come in immediate contact, but also enter in a 

 loose combination with the protoplasm, and must pass 

 into the interior of the cells, or whether the decomposi- 

 tion can take place outside the cells, and whether less 

 intimate contact of the protoplasm with the fermen- 

 tescible materials is sufficient for their decomposition? 

 According to experiments made by Cochin* it can be 



* Cochin, Compt. rend , vol. 96. 



40 



