PART IV 
DAIRY BACTERIOLOGY 
Exercise 25. The Bacteriological Examination of Milk 
MATERIALS: 
11 tubes of lactose agar 
11 sterile Petri dishes 
3 99 c.c. water blanks 
4 9 c.c. water blanks 
Case sterile pipettes 
Sample of high-grade milk 
Sample of market milk 
Milk that is to be examined must be well mixed. Creaming and settling 
have some effect upon the distribution of bacteria in milk. 
FIG. 18—DIAGRAM OF THE DILUTIONS FOR ORDINARY MARKET MILK 
