TO FERMENTATION. 109 



mentation, or putrefaction, may be described as a 

 process of transformation that is, a new arrange- 

 ment of the elementary particles, or atoms, of a 

 compound, yielding two or more new groups or 

 compounds, and caused by contact with other sub- 

 stances, the elementary particles of which are them- 

 selves in a state of transformation or decomposition. 

 It is a communication, or an imparting of a state of 

 motion, which the atoms of a body in a state of 

 motion are capable of producing in other bodies, 

 whose elementary particles are held together only 

 by a feeble attraction. 



8. Thus the clear gastric juice contains a sub- 

 stance in a state of transformation, by the con- 

 tact of which with those constituents of the food 

 which, by themselves, are insoluble in water, the 

 latter acquire, in virtue of a new grouping of 

 their atoms, the property of dissolving in that fluid. 

 During digestion, the gastric juice, when separated, 

 is found to contain a free mineral acid, the presence 

 of which checks all further change. That the food is 

 rendered soluble quite independently of the vitality 

 of the digestive organs has been proved by a num- 

 ber of the most beautiful experiments. Food, en- 

 closed in perforated metallic tubes, so that it could 

 not come into contact with the stomach, was found 

 to disappear as rapidly, and to be as perfectly di- 

 gested, as if the covering had been absent; and 

 fresh gastric juice, out of the body, when boiled 

 white of egg, or muscular fibre, were kept in 



