YEAST OR FERMENT. 289 



fermentation. Both were decomposed at the same time; the 

 nitrogen of the azotized compounds remains in the liquid as am- 

 monia, and, in addition to it, there are three new products, formed 

 from the component parts of the juice. One of these is lactic 

 acid, the slightly volatile compound found in putrid animal mix- 

 tures ; the other is the crystalline body which forms the principal 

 constituent of manna ; and the third is a mass resembling gum- 

 arabic, which forms a thick viscous solution with water. These 

 three products weigh more than the sugar contained in the juice, 

 even without calculating the weight of the gaseous products. 

 Hence they are not produced from the elements of the sugar 

 alone. None of these three substances could be detected in the 

 juice before fermentation. They must, therefore, have been 

 ibrmed by the interchange of the elements of the sugar with 

 those of the foreign substances also present. It is this mixed 

 transformation of two or more compounds which receives the 

 special name of putrefaction. 



YEAST OR FERMENT. 



When attention i;> directed to the condition of those substances 

 which possess the power of inducing fermentation and putre- 

 faction in other bodies, evidence is found in their general 

 characters, and in the manner in which they combine, that 

 they all are bodies, the atoms of which are in the act of trans- 

 position. 



The characters of the remarkable matter deposited in an inso. 

 iuble state during the fermentation of beer, wine, and vegetable 

 juices, may first be studied. 



This substance, called yeast or ferment, from the power 

 which it possesses of causing fermentation in sugar, or saccha- 

 rine vegetable juices, possesses all the characters of a com- 

 pound OF NITROGEN IN THE STATE OF PUTREFACTION AND ERBMA- 

 CAUSIS. 



14 



