CHAPTER II. 
BACTERIA AND MILK FERMENTATIONS. 
A thorough knowledge of bacteria and their relation 
to milk and milk products forms the basis of success in 
the handling of milk and cream as well as in butter and 
cheese making. 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. ge 
Bacteria grow with mafvelous 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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