622 VITAL ACTIONS OF THE LOWEK FUNGI. - 



mentation of the glucoses, where three carboxyl com- 

 binations are present in the six C atoms, and lead to 

 the breaking up of the relatively large molecule. For the 

 same reason fermentation of acetic acid is very difficult, 

 and of propionic acid still more difficult ; for here, as in 

 the case of formic acid, there is only one atom which 

 can be utilised for the formation of carboxyl, while the 

 molecule itself is much larger. On the other hand, fer- 

 mentation can occur more readily in the oxy-acids 

 (glycollic acid, lactic acid, &c.), because in these there 

 exists a second hydroxyl group, and thus a second dis- 

 placeable atom. Accordingly, the following sub- 

 stances are not at all capable of fermentation : carbu- 

 retted hydrogen, amines which do not contain any oxygen ; 

 further, the large molecules of the higher fatty acids, 

 and of the benzole derivatives which are poor in oxygen 

 (the latter only in regard to the benzole portion, while, 

 naturally, in the side groups, splitting up and wander- 

 ing of oxygen can occur). On the other hand the fol- 

 lowing, among other substances, must be capable of 

 fermentation : the higher alcohols, the lower uni-basic 

 fatty acids, up to propionic acid, the oxy-acids, and the 

 multi-basic acids of the fatty series, the carbo-hydrates, 

 and the albuminoid materials. 



The dccompo- Hence without extensive displacement of the atoms, 

 sition of the no fermentation is conceivable, and it is by this in- 

 this case is tense alteration of the fermentescible molecules that 

 th?a r c e t^on fr o f m the true fermentations are chiefly distinguished from 

 enzymes. fa e hydrolytic decompositions caused by isolated fer- 

 ments. All fermentations are direct results of the func- 

 tional activity of micro-organisms, and it is not only 

 absolutely certain, from the experiments previously 

 described, that fermentation never occurs without living 

 organisms, but we must also free ourselves from the 

 idea that the fermentative action results from the pro- 

 duction of a ferment which cannot be separated from 

 the micro-organism without interfering with its life. 

 The intimate process of fermentation shows so much 

 that is different from that of the action of enzymes, and 

 shows, on the other hand, such an intimate connection 



