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. 



FIG. 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. (Bui. 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 



