Slime Moulds, Bacteria, and Yeasts. 263 



at the same time is driven off in the process of baking. If 

 the bread is allowed to stand too long before baking, the 

 alcohol is attacked by bacteria which change it into acids, 

 and the dough is soured. 



161. Yeasts in Alcoholic Fermentation. — There are vari- 

 ous sorts of yeasts which produce alcohol, and some other 

 little-known substances that give flavor, bouquet, etc., in the 

 manufacture of beer, wine, and other fermented liquors. 

 In recent years these various kinds of yeasts have been 

 grown separately, and are used in the production of distinct 

 kinds of beer and wine. Some yeasts seem also to be the 

 cause of disease in man and the lower animals. 



