FERMENTATION. 257 



found incased in ice. It had been buried for ages, but 

 when laid bare its flesh was sweet, and for some time 

 afforded copious nutriment to the wild beasts which fed 

 upon it. 



Beer is assailable by all the organisms here referred 

 to, some of which produce acetic, some lactic, and some 

 butyric acid, while yeast is open to attack from the 

 bacteria of putrefaction. In relation to the particular 

 beverage the brewer wishes to produce, these foreign 

 ferments have been properly called ferments of disease. 

 The cells of the true leaven are globules, usually some- 

 what elongated. The other organisms are more less 

 rod-like or eel-like in shape, some of them being beaded 

 so as to resemble necklaces. Each of these organisms 

 produces a fermentation and a flavour peculiar to itself. 

 Keep them out of your beer and it remains for ever 

 unaltered. Never without them will your beer contract 

 disease. But their germs are in the air, in the vessels 

 employed in the brewery; even in the yeast used to 

 impregnate the wort. Consciously or unconsciously, the 

 art of the brewer is directed against them. His aim is 

 to paralyse, if he cannot destroy them. 



For beer, moreover, the question of temperature is 

 one of supreme importance ; indeed, the recognized 

 influence of temperature is causing on the Continent 

 of Europe a complete revolution in the manufacture of 

 beer. When I was a student in Berlin, in 1851, there 

 were certain places specially devoted to the sale of 

 Bavarian beer, which was then making its way into 

 public favour. This beer is prepared by what is called 

 the process of loiv fermentation ; the name being given 

 partly because the yeast of the beer, instead of rising 

 to the top and issuing through the bunghole, falls to 

 the bottom of the cask ; but partly, also, because it is 

 produced at a low temperature. The other and older 



