Requirements 

 for Growth 



40 



HOUSEHOLD BACTERIOLOGY. 



Thus the generations are continued and the individuals 

 multiplied. 



Yeast requires food, oxygen, warmth, and moisture. 

 Sugary substances are especially liked by the yeast 

 which is used to make bread. This is a specially cul- 

 tivated form of brewer's yeast. Yeast directly from 



TYPICAL FOEMS AND APPEARANCE OF BREWERS- 

 YEAST. (After Sedgwick and Wilson.) 



Products 

 of Growth 



the breweries is often used for breadmaking. It 

 is while feeding upon these sugary solutions that 

 the tiny plants bring about the chemical changes by 

 which alcohol and the gas, carbon dioxide, are pro- 

 duced. The gas puffs up the dough and makes pos- 



