CHAPTER XII 

 MAY BE CULTIVATED 



EVERY one knows that all domestic animals, 

 horse, cow, sheep, dog, and the rest, including all 

 domestic fowls, were once wild at least their 

 ancestors were wild. Man has captured, tamed 

 and domesticated them. By long processes of cul- 

 ture he has greatly improved and added to them 

 many new species and varieties. 



Every one knows, too, that all our domestic 

 plants, corn, wheat, oats, rye, barley, and the rest, 

 including all our vegetables, and flowers from the 

 garden, were likewise once wild. Man has trans- 

 planted and domesticated them. From times im- 

 memorial he has cultivated them, and by the long 

 processes of natural selection he has multiplied 

 many times the original species and varieties 

 whence they came, and greatly improved them all. 



But not every one knows that man sustains a 

 similar relation to micro-organisms. Such, how- 

 ever, is the fact. In their original state they, too, 

 in a sense, are wild. They, too, may be captured 

 and domesticated, the good becoming better, the 

 bad, if possible, worse. From time immemorial 

 the baker's yeast, in the solid or liquid form, has 

 been a culture for the microbes of bread. From 



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