FERMENTATION. 99 



in Germany, Austria, and Scandanavia, and also in France, 

 the low fermentation has now almost entirely ousted the high 

 form. There can be little doubt that this is due, in part at 

 any rate, to the impetus that Pasteur's studies gave to the 

 subject of the careful examination of yeast ; he pointed out 

 that at the higher temperature there was greater danger of 

 contamination by organisms which produce other fermenta- 

 tions than the alcoholic, and that these micro-organisms 

 unable to flourish at the lower temperature, would at the 

 higher temperature grow most luxuriantly. This of course is 

 undoubtedly true, but it should be remembered that where 

 the brewing is in the hands of men in a small way of business 

 the conditions are very different from those where all the 

 apparatus and skill that capital can command are at the 

 disposal of the brewer. If it were once known which was the 

 best kind of yeast for high beer fermentation it would be 

 possible to obtain pure cultivations, and with it so to conduct 

 the beer fermentation by attending most carefully to the 

 cleanliness of the vessels in which beer is made and stored as 

 to obtain a very pure beer, having excluded all organisms that 

 by their fermentation miglit render it unsound. The low beer 

 may be brewed in smaller quantities and under less favourable 

 conditions as regards the possibility of keeping the yeast pure 

 than at higher temperatures. The yeast then used causes the 

 fermentation to go on at such a low temperature, that a large 

 number of the organisms which usually give rise to impurity in 

 the beer cannot multiply. Such beer, however, can only be 

 stored when the temperature is kept very low, for as soon as 

 this begins to rise the dormant spores of other organisms 

 begin to develop, set up various acid fermentations and spoil 

 the beer. The different methods of brewing are also deter- 

 mined in part at any rate by the climates of the different 

 countries the cool, light beer apparently being more palatable 

 in warm continental countries ; the heavier, with its own 

 peculiar flavour, being usually more sought after in this 

 country. 



Given pure yeasts, thorough cleanliness, and means of 

 keeping out other organisms, both beers may be kept sound 

 even though the temperature be comparatively high. To 

 obtain such pure yeast it is necessary first to take a single 

 cell, and from this to grow a series of buds and chains in a 

 sterilized wort, to break this up into separate portions of seed 



