CHAPTER IV. 



BACTERIA AND MILK FERMENTATIONS. 



A thorough knowledge of bacteria and their action 

 forms the basis of success in butter making. Indeed the 

 man who is lacking such knowledge is making butter 

 in the dark; his is chance work. Much attention will 

 therefore be given to the study of these organisms in 

 this work. 



I. BACTERIA. 



The term bacteria is applied to the smallest of living 

 plants, which can be seen only under the highest powers 

 of the miscroscope. Each bacterium is made up of a 

 single cell. These plants are so small that it would 

 require 30,000 of them laid side by side to measure an 

 inch. Their presence is almost universal, being found 

 in the air, water, and soil ; in cold, hot, and temperate 

 climates; and in living and dead as well as inorganic 

 matter. 



Bacteria grow with marvelous rapidity. A single bac- 

 terium is capable of reproducing itself a million times 

 in twenty- four hours. They reproduce either by a simple 

 division of the mother cell, thus producing two new cells, 

 or by spore formation in which case the contents of the 

 mother cell are formed into a round mass called a spore. 

 These spores have the power of withstanding unfavorable 

 conditions to a remarkable extent, some being able to 

 endure a temperature of 212 F. for several hours. 



Most bacteria require for best growth 'a moist, warm, 

 and nutritious medium such as is furnished by milk, in 



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