606 VITAL ACTIONS OF THE LOWER FUNGI. 



of saprophytes. This test, however, has almost never 



heen employed. 



Fcrmenta- Thus on the whole we have very few certain facts as 



pioyedTii the * * ne m de in which the decompositions are brought 

 preparation of a b ou t hy certain species of bacteria. Hence it is that 



food. * . 



we are, as yet, very imperfectly informed as to many 

 of the most frequent fermentative processes which spon- 

 taneously occur, or are artificially set up in our surround- 

 ings, for example, in the preparation of food, in many 

 Fermentation manufactures, &c. Even as regards the cause, the 

 course, and the products of the fermentation of bread, 

 we know very little that is trustworthy. It is very pro- 

 bable that the rising of the leaven is not caused by a 

 pure yeast fermentation, for, especially in leaven, 

 bacteria are present in preponderating numbers. Ac- 

 cording to the more recent investigations of Chicandard,* 

 yeast does not play any part, or only a very secondary 

 one, in the fermentation of bread, and the true agent 

 seems to be rather a species of bacterium. Marcanot 

 also sees in the mobile bacteria the true cause of the 

 fermentation of bread, while BontrouxJ is of opinion 

 that in this process several kinds of organisms, varieties 

 of yeast, and bacteria play an active part. It would be 

 very desirable to obtain information as to this daily 

 fermentative phenomenon by means of accurate experi- 

 ments made with the aid of the more recent bacterio- 

 logical methods. 



In some cases combinations of fermentations are em- 

 ployed in the preparation of nutrient materials, especially 

 in order to obtain the formation of aethylic alcohol by 

 means of yeast from materials which are not in reality 

 fermentescible, for example, from starch, dextrine, milk- 



* Chicandard, Compt. rend., vols. 96, 97. t Marcano, ibid. 



J Bontroux, ibid., vol. 97. Moussette, ibid., vol. 96. 



Duclaux has made minute investigations as to the bacteria which 

 grow in milk and in cheese, and which take part in the decompositions 

 which occur; he designates them under the generic name tyrothrix, 

 and distinguishes T. scaber, T. tenuis, T. filiformis, &c. Unfortu- 

 nately the papers in which these results are given in detail (Annals de 

 rinstit. agron., and Duclaux's Chimie bioloyique} could not be obtained 

 in the libraries in Gottingen and Berlin, and only became known to the 

 author at too late a period to be utilised in this work. 



