STUDIES ON FERMENTATION. 321 



and which resembles that which sugar undergoes. I have shown 

 that malate of lime ferments readily enough through the action 

 of yeast, and that it splits up into three otlier calcareous salts, 

 namely, the acetate, the carbonate, and the succinate. If the 

 action of yeast consists in its increase and multiplication, it is 

 difficult to conceive this action in the case of malate of lime 

 and other calcareous salts of vegetable acids." 



This statement, with all due deference to the opinion of our 

 illustrious critic, is by no means correct. Yeast has no action 

 on malate of lime, or on other calcareous salts formed by vege- 

 table acids. Liebig had previously, much to his own satisfac- 

 tion, brought forward urea as being capable of transformation 

 into carbonate of ammonia during alcoholic fermentation in con- 

 tact with yeast. This has been proved by us to be erroneous. 

 It is an error of the same kind that Liebig again brings forward 

 here. In the fermentation of which he speaks (that of malate 

 of lime), certain spontaneous ferments are produced, the germs 

 of which are associated with the yeast, and develop in the mix- 

 ture of yeast and malate. The yeast merely serves as a source 

 of food for these new ferments without taking any direct part 

 in the fermentations of which we are speaking. Our researches 

 leave no doubt on this point, as is evident from the observations 

 on the fermentations of tartrate of lime previously given. 



It is true that there are circumstances under which yeast 

 brings about modifications in different substances. Doebereiner 

 and Mitscherlich, more especially, have shown that yeast im- 

 parts to water a soluble material, which liquefies cane-sugar 

 and produces inversion in it by causing it to take up the 

 elements of water, just as diastase behaves to starch or emulsin 

 to amygdalin. 



M. Berthelot also has shown that this substance may be 

 isolated by precipitating it with alcohol, in the same way as 

 diastase is precipitated from its solutions.* These are remark- 



* Doebereiner, Journal de CJnmie de Schweigger, vol. xii. p. 129, and 

 Journal de Pharmade, vol. i. p. 342. 



Mitscherlich, Monatsherkhte d. Kon.Preuss. Akad. d. JVissen. zu Berlin^ 



Y 



