24 



vored food present in the stable during milking, such as silage (refer- 

 ences No. 3, p. 25; No. 8, p. 13, and No. 10, p. 104). 



5. Injurious flavors from bacterial infection. — The most common 

 source of milk contamination is from bacteria. These get into the 

 milk ducts of the udder and contaminate the first milk drawn (ref- 

 erences No. 9, p. 36, and No. 11, p. 39). After the milk is drawn bac- 

 teria get into it (1) from the cow (references No. 9, p. 44, and No. 11, 

 p. 41); (2) from the air (references No. 9, p. 43, and No. 11 , p. 45); 

 (3) from the milk vessels (references No. 9, p. 44, and No. 11 , p. 34), 

 and (4) from the milkers (references No. 3, p. 24; No. 9, p. 44, and 

 No. 11, p. 41). 



6. Characteristics of hacteria. — Bacteria are very small, colorless 

 plants, invisible to the unaided eye. They are extremely numerous 

 and widely cUstributed in soil, air, and water. In shape they are 

 spherical, rod-shaped, and spiral (references No. 9, p. 20, and 

 No. 11, p. 2). They multiply by simple division ^\ath great rapidity 

 (references No. 9, p. 26, and No. 11, p. 4). Bacteria require as 

 food compounds containing nitrogen, carbon, hydrogen, oxygen, and 

 inorganic matter (references No. 9, p. 28, and No. 11, p. 7). The 

 sugar, casein, and albumin in milk and its products furnish avail- 

 able food for bacteria. Bacteria grow only within certain ranges of 

 temperature, the most favorable temperatures being between 80° and 

 95° F. for those common in milk (references No. 9, p. 29, and No. 

 11, p. 8). All bacteria are destroyed at the temperature of boiling 

 water (reference No. 9, p. 29) and by many chemical substances called 

 antiseptics (reference No. 11, p. 18). Bacteria are always associated 

 with filth, absence of sunlight, and impure air. 



7. Obtaining clean milk. — Milk produced for use in cheese making 

 should be kept fairly free from bacteria, and the rapid growth of 

 those in the milk should be retarded. The number of bacteria in 

 milk can be largely' reduced by the following precautions: (1) Every 

 condition in and about the stable should be regulated with reference 

 to an abundant supply of pure air, a direct exposure to sunlight, and 

 the absence of dust or any form of dirt. No manure or stagnant 

 water should be near the barn. The barnyard should be distant 

 from the milking stall (reference No. 9, p. 48). (2) Keep the body 

 of the cow as free as possible from every form of dirt, dust, and 

 loose hairs (reference No. 9, p. 47). (3) Before milking, the cow's 

 udder should be properly cleaned and the milker should have clean 

 hands and clothing (reference No. 9, p. 44). (4) The milk vessels 

 must be kept bacteriologically clean (reference No. 9, p. 44). The 

 water used in washing vessels should be free from unhealthful con- 

 taminations (reference No. 9, p. 51). (5) Milk pails should be 

 used olTering the least exposure of surface of milk (reference No. 9, 

 p. 52). (6) After milking a pailful remove the milk from the barn 



