yo Putrid Fermentation. [Book VIII, 



rnation of other acids, as by the following direct ex- 

 periments. In the firft place, we cannot change wine 

 into vinegar, without expofing the former to the con- 

 tact of air containing oxygen, or employing fome other 

 mode of oxygenation; fecondly, this procefs is accom- 

 panied by a diminution of the volume of the air in 

 which it is carried on, from the abforption of oxygen ; 

 and thirdly, wine, by being converted into vinegar, is 

 increafed in weight. 



The PUTRID FERMENTATION is the deftruction of 

 the equilibrium which holds the conftituent principles 

 of bodies in a ftate of combination. Thus a vegetable 

 fubftance, which when entire confifts of a triple com- 

 bination of hydrogen, oxygen, and carbon, is refolved 

 by putrefaction into hydrogen gas, and carbonic acid 

 gas, which confifts of oxygen and carbon. As there 

 is not enough of oxygen to convert all the carbon into 

 carbonic acid gas, a quantity of the charcoal remains 

 behind, mixed with the earthy and faline matter con- 

 tained in the vegetable. Thus putrefaction in a vege- 

 table fubftance, is nothing more than a complete ana- 

 lyfis of it, in which the conftituent elements aredifen- 

 gaged in the form of gas, except the earth, and a 

 quantity of charcoal which remains in the ftate of 

 mould. 



Such is the refult of putrefaction when the fubftances 

 fubmitted to it contain only oxygen, hydrogen, char- 

 coal, and a little earth. Hut this cafe is rare; and 

 thefe fubftances putrefy imperfectly, and with difficulty. 

 It is otherwife with fubftances containing azote, which 

 indeed exifts in all animal matters, and in a confider- 

 able number of vegetables. The putrid ferment mon 

 of animal fubftances is commonly called putrefaction, 

 and this, is well known to take place in them, after they 

 are deprived of life. The circumftances which favour 



putre- 



