ALCOHOL AND CARBON DIOXIDE 95 



and (3) to get a fresh supply of yeast. After this the 

 trouble ought to disappear. It is also important to 

 remember that the sliminess only occurs if the bread is 

 kept warm, and hence chiefly in the summer. If the 

 bread is cooled at once and kept in a cool place until it is 

 eaten, the trouble is not likely to manifest itself even 

 though the slimy bacteria are present. The bread is 

 wholesome enough even though slimy. 



THE UTILIZATION OF BOTH ALCOHOL AND CARBON 

 DIOXIDE 



In the immense fermentation industries involving the 

 production of beers, porters, ales, etc., both of the products 

 of fermentation are commonly utilized. The general char- 

 acter and effect of beer are due partly to the alcohol pres- 

 ent and partly to the presence of a quantity of the car- 

 bon dioxide, which gives to the beer its sparkle. In the 

 manufacture of such a product the fermentable material, 

 usually some form of grain, is inoculated with a large 

 quantity of a vigorous yeast, a species being chosen that 

 has been found by experience to produce the desired 

 results. A fermentation starts up which progresses rap- 

 idly if the temperature is kept warm, as it is in the man- 

 ufacture of common beer. The fermentation lasts a few 

 days. If the temperature is low, as in the production of 

 the so-called lager beer, the fermentation lasts many weeks. 

 During this fermentation alcohol accumulates in the liquid, 

 and the carbon dioxide gas escapes into the air, forming 

 a froth in the fermenting vat. The yeast increases in 

 amount, and either collects on the surface or sinks to 



