520 Frofesaor Percy F. Franhland [Feb. 19, 



was an imconscious author of prose. It was Pasteur also who first 

 infused science into the operations of the wine-vat and the ferment- 

 ing-tun, by his classical ' Etudes sur la Biere et sur le Vin.' It was 

 he who first showed that the normal work of the brewery was accom- 

 plished by particular forms of micro-organisms, known as yeast, and 

 that the frequent failures to produce beer or wine of the desired 

 quality were occasioned by the presence of foreign forms of micro- 

 organisms giving rise to acidity and other undesirable changes in 

 these beverages. 



In these researches of Pasteur's on beer and wine, we are almost 

 for the first time brought face to face with the precise nature of some 

 of the chemical changes which micro-organisms bring about. The 

 time-honoured vinous fermentation of sugar, the products of which 

 had been valued and indulged in by man even from the days of Noah, 

 is for the first time so accurately studied as to be definable almost 

 with the precision of a chemical equation. 



Similar attention was also given by Pasteur to some of the other 

 micro-organisms which deteriorate the quality of the beer, thus more 

 especially to the bacterium which causes the acetic or vinegar fer- 

 mentation, which is a process of oxidation, transforming alcohol into 

 vinegar ; to the bacillus inducing the lactic fermentation, which is a 

 process of decomposition, in which sugar yields lactic acid ; as well as 

 to that which brings about the butyric fermentation, a process of 

 reduction in which butyric acid is formed. 



These are the foundations and scaffolding on which subsequent 

 investigators of the phenomena of fermentation have laboured. Thus 

 making use of more refined methods than those which were at the 

 disposal of Pasteur, Christian Hansen, of Copenhagen, has enor- 

 mously extended our knowledge of the alcohol-producing organisms 

 or yeasts ; he has shown that there are a number of distinct forms, 

 differing indeed but little amongst themselves in shape, but possess- 

 ing very distinct properties, more especially in respect of the nature 

 of certain minute quantities of secondary products to which they give 

 rise, and which are highly important as giving particular characters 

 to the beers produced. Hansen has shown how these various kinds of 

 yeast may be grown or cultivated in a state of purity even on the 

 industrial pcale, and has in this manner revolutionised the practice 

 of bi ewing on the Continent. For during the past few years these 

 pure yeasts, each endowed with particular properties, have been 

 grown with scrupulous care in laboratories equipped expressly for 

 this purpose, and these pure growths are thence despatched to 

 breweries in all parts of the world, particular yeasts being provided 

 for the production of particular varieties of beer. In this manner 

 scientific accuracy and the certainty of success are introduced into 

 an industry in which before much was a matter of chance, and in 

 which nearly everything was subordinated to tradition and blind 

 empiricism. 



