GAY-LUSSAC'S OPINION. 13 



STAHL (I.), deserves mention, because his views on the nature of 

 fermentation were adopted by Liebig a hundred and forty years 

 later. Stahl extended the definition of fermentation to all forms 

 of decomposition, his theory being expressed verbatim as follows : 

 " Putrefaction (and also fermentation) is internal movement. A 

 body undergoing such internal movement may easily induce the 

 same in any other body, which, though still quiescent, is sus- 

 ceptible of such movement." 



11. Gay-Lussac's Opinion. 



Stahl's view remained in vogue until the commencement of 

 the present (iQth) century, when Gay-Lussac, in 1810, enunciated 

 a new theory to a new age. The discovery by Lavoisier that 

 combustion is a process of oxidation, a combination of oxygen 

 with the combustible substance, was an event the influence 

 whereof extended over the entire domain of chemistry. The 

 assignment to oxygen of a part in the process of fermentation 

 was therefore opportune; but Gay-Lussac was especially prompted 

 by another circumstance. 



A Parisian confectioner and cook, named Appert, had made 

 practical use of the experiment devised by his contemporary 

 Spallanzani for the refutation of the heterogenists, and, after 

 some preliminary trials, perfected his process for preserving meats, 

 vegetables, spirituous liquors, &c. To this end he exposed them, 

 in hermetically closed vessels, to the temperature of boiling water 

 for some time a process which had somewhat earlier (1782) 

 been recommended by the Swedish chemist SCHEELE (I.) for 

 the conservation of vinegar. In this way APPERT founded a 

 new branch of industry the manufacture of conserves which 

 brought him both wealth and fame. He published a volume (I.) 

 which comprised the results of his experience. It was widely 

 circulated and ran into several editions, the first of which appeared 

 in 1 8 10, and the fourth in 1831. 



It is therefore little matter for surprise that the attention of 

 the Parisian chemist was directed (whether from the culinary or 

 the literary side) to the productions of his enterprising fellow- 

 citizen. GAY-LUSSAC (I.) now examined conserves prepared accord- 

 ing to Appert's process, and found them to be free from gaseous 

 oxygen. This incited him to make fermentation experiments 

 with wine-must, &c., the results of which led him to assert that 

 the presence of oxygen is necessary to the inception of fermenta- 

 tion. A number of over-zealous colleagues, in expounding their 

 master's opinion, added new features to it, and subsequently 

 credited him with the assertion that oxygen is the actual ferment 

 a statement as unfounded as it is inaccurate. Gay-Lussac only 

 claimed for the gas a single function, the inception of fermenta- 

 tion ; once the process was in operation the stimulus was no 



