FERMENTATION 287 



some of which produce acetic, some lactic, and some bu- 

 tyric 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 somewhat elongated. 

 The other organisms are more or less rod-like or eel-like 

 in shape, some of them being beaded so as to resemble 

 necklaces. Each of these organisms produces a fermenta- 

 tion and a flavor peculiar to itself. Keep them out of 

 your beer and it remains forever unaltered. Never with- 

 out 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. Con- 

 sciously or unconsciously, the art of the brewer is directed 

 against them. His aim is to paralyze, if he cannot anni- 

 hilate 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 favor. This 

 beer is prepared by what is called the process of low fer- 

 mentation; 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 process, called high fermentation^ is far 

 more handy, expeditious, and cheap. In high fermenta- 

 tion eight days suffice for the production of the beer; in 



