FERMENTS IN MILK. 51 
is a number of species belonging to this group. The patho- 
genic germs, or disease-producing bacteria, must also be classed 
with the harmful bacteria. It is not the intention in this 
work to give an extended discussion of this subject. For 
such discussion see special works on Dairy Bacteriology. 
Fic. 10-—Shows plate exposed one-half minute under cow’s udder treated 
by merely brushing with the hand; each little spot represents a colony 
of some kind of bacteria. (Bul. 87, Nebraska.) 
Number of Bacteria in Milk.—The number of bacteria 
found in milk varies so much that it is practically impossible 
to state accurately the average number. The number of 
germs found varies according to several conditions, such as 
degree of cleanliness of cows, utensils, and milker; degree of 
purity of the atmosphere when the cows are milked; and 
the temperature at which the milk is kept. When the milk 
is being produced under the best practical sanitary conditions, 
the number of germs need not exceed 10,000 per c.c. Such 
