76 CRITIQUES AND ADDRESSES. [iv. 



the presence of sugar was essential to the production of 

 alcohol and the evolution of carbonic acid gas, which are 

 the two great and conspicuous products of fermentation. 

 And finally, in 1787, the Italian chemist, Fabroni, made 

 the capital discovery that the yeast ferment, the presence 

 of which is necessary to fermentation, is what he termed 

 a " vegeto-animal " substance or is a body which gives 

 off ammoniacal salts when it is burned, and is, in other 

 ways, similar to the gluten of plants and the albumen 

 and casein of animals. 



These discoveries prepared the way for the illustrious 

 Frenchman, Lavoisier, who first approached the problem 

 of fermentation with a complete conception of the nature 

 of the work to be done. The words in which he ex- 

 presses this conception, in the treatise on elementary 

 chemistry to which reference has already been made, 

 mark the year 1789 as the commencement of a revolu- 

 tion of not less moment in the world of science than 

 that which simultaneously burst over the political world, 

 and soon engulfed Lavoisier himself in one of its mad 

 eddies. 



" We may lay it down as an incontestable axiom that, in all the 

 operations of art and nature, nothing is created ; an equal quantity of 

 matter exists both before and after the experiment : the quality and 

 quantity of the elements remain precisely the same, and nothing takes 

 place beyond changes and modifications in the combinations of these 

 elements. Upon this principle, the whole art of performing chemical 

 experiments depends ; we must always suppose an exact equality 

 between the elements of the body examined and those of the products 

 of its analysis. 



" Hence, since from must of grapes we procure alcohol and carbonic 

 acid, I have an undoubted right to suppose that must consists of car- 

 bonic acid and alcohol. From these premisses we have two modes of 

 ascertaining what passes during vinous fermentation : either by deter- 

 mining the nature of, and the elements which compose, the ferment- 

 able substances ; or by accurately examining the products resulting 

 from fermentation ; and it is evident that the knowledge of either of 

 these must lead to accurate conclusions concerning' the nature and com- 



