50 BUTTER-MAKING. 
For this purpose, it is sufficient to classify the bacteria into 
three groups; viz., (1) those which are harmful to the butter- 
making industry, (2) those which are beneficial, and (3) those 
which are indifferent, or produce neither good nor bad results. 
From the farmer’s or milk-producer’s standpoint, none 
of these bacteria are desirable. Each milk-producer should 
Fic. 9.—Shows a plate exposed one-half minute under a cow’s udder treated 
with a 5% solution of carbolic acid. (Bul. 87, Nebraska.) 
make it a point to prevent their entrance and suppress their 
development in milk and cream to as great an extent as pos- 
sible. The creamery operator should endeavor to suppress 
all of the harmful germs, and foster the development of the 
desirable ones. 
The germs which are desirable belong chiefly to the acid- 
producing types. They are often called lactic ferments. 
The harmful bacteria include those which produce bitter 
milk, red milk, blue milk, yellow milk, slimy milk, etc. There 
