THE UNIVERSE OP LITTLE THINGS. 213 
Fig. 107.—Soil bacteria 
which prepare nitro¬ 
gen for plants in soils 
where there is a lack 
of it. 
Bacteria are useful agents in 
preparing the soil, in maintain¬ 
ing its fertility, in clearing away 
filth, in the preparation of foods 
and drinks; in short, they touch 
man in all his interests. Without 
bacteria butter could not have the 
fiavor so much to our taste, and 
cheese would be but a poor diet. 
Milk is a good medium for bacteria to thrive in. 
Some are usually in the pail; the cow has them on her 
hair and skin, and particularly in 
the filth that clings to her; they 
are in the dust of the hay; and 
thus before the milk reaches the 
house many kinds have made a 
good start in the warm liquid, 
which is rich in bacterium food 
and at a temperature favorable to 
their development. The milkman is often wrongfully 
accused of watering his milk 
when it has a bluish cast. 
This is due not to water, 
but to harmful bacteria liv¬ 
ing in the milk. The most 
harmful kind in milk is 
that which produces tuber¬ 
culosis. 
The remedy is healthy 
Pig. 108.—Dairy bac¬ 
terium producing 
red milk. 
COWS, cleanliness in food 
and water, in the stable, in 
15 
Fig. 109.—Bacteria cultivated 
in scientific creameries for 
the purpose of ripening 
cream in order to give but¬ 
ter a pleasant fiavor. 
