236 FERMENT A T/Otf 



As soon as man learned that yeast plants caused fermenta- 

 tion in liquors and bread, he realized that it would be to his 

 advantage to cultivate yeast and to add it to bread and to 

 plant juices rather than to depend upon accidental and slow 

 fermentation from wild yeast. Shortly after the discovery of 

 yeast in the nineteenth century, man commenced his attempt 

 to cultivate the tiny organisms. Their microscopic size added 

 greatly to his trouble, and it was only after years of careful 

 and tedious investigation that he was able to perfect the 

 commercial yeast cakes and yeast brews universally used by 

 bakers and brewers. The well-known compressed yeast cake 

 is simply a mass of live and vigorous yeast plants, embedded in 

 a soft, soggy material, and ready to grow and multiply as soon 

 as they are placed under proper conditions of heat, moisture, 

 and food. Seeds which remain on our shelves do not germi- 

 nate, but those which are planted in the soil do ; so it is with 

 the yeast plants. While in the cake they are as lifeless as 

 the seed ; when placed in dough, or fruit juice, or grain water, 

 they grow and multiply and cause fermentation. 



