YEASTS A SOURCE OF ALCOHOL 69 



As Friends. Yeasts must usually be looked upon as 

 servants rather than as enemies. They are the allies of 

 the housewife in a number of directions. J^e have 

 noticed above that when they grow in sugar solutions 

 they give rise to two new substances, carbon dioxide and 

 alcohol, and in various domestic affairs sometimes the 

 one, sometimes the other, and_ sometimes both of these 

 products are utilized. 



The Use of Yeasts as a Source of Alcohol 



The alcohol produced by yeasts is the foundation of the 

 great fermentative and distillery industries, for common 

 yeasts are the agents which produce the alcohol found in 

 all alcoholic beverages. The fermentative industries, of 

 immense extent all over the civilized world, are dependent 

 upon yeasts. In the manufacture of fermented and dis- 

 tilled liquors these little plants are used in all cases for 

 the production of alcohol out of various sugar solutions. 

 The fermentative industries, therefore, involving the invest- 

 ment of hundreds of millions of dollars, are founded upon 

 the growth and powers of these microscopic plants. The 

 struggle with gigantic evils resulting from these industries 

 forms one of the greatest problems of civilization. This, 

 however, is a matter which does not belong to our 

 immediate subject. 



In breweries and distilleries some material containing 

 sugar (molasses, preparations from rye, corn, barley, etc.) 

 is inoculated with a quantity of yeast, a species being 

 chosen which experience has shown to be well adapted 

 to the purpose. The mixture is warmed slightly and a 



