120 NATURE OF FERMENT. 



All substances which can arrest the phenomena 

 of fermentation and putrefaction in liquids, also ar- 

 rest digestion when taken into the stomach. The 

 action of the empyreumatic matters in coffee and 

 tobacco-smoke, of creosote, of mercurials, &c. &c., is 

 on this account worthy of peculiar attention with 

 reference to dietetics. 



The identity in composition of the chief consti- 

 tuents of blood and of the nitrogenised constituents 

 of vegetable food has certainly furnished, in an un- 

 expected manner, an explanation of the fact that 

 putrefying blood, white of egg, flesh, and cheese pro- 

 duce the same effects in a solution of sugar as yeast 

 or ferment ; that sugar, in contact with these sub- 

 stances, according to the particular stage of decom- 

 position in which the putrefying matters may be, 

 yields, at one time, 'alcohol and carbonic acid ; at 

 another, lactic acid, mannite, and mucilage. The 

 explanation is simply this, that ferment, or yeast, 

 is nothing but vegetable fibrine, albumen, or caseine 

 in a state of decomposition, these substances having 

 the same composition with the constituents of flesh, 

 blood, or cheese. The putrefaction of these animal 

 matters is a process identical with the metamorpho- 

 sis of the vegetable matters identical with them ; 

 it is a separation or splitting up into new and less 

 complex compounds. And if we consider the trans- 

 formation of the elements of the animal body (the 

 waste of matter in animals) as a chemical process 

 which goes on under the influence of the vital force, 



