286 BACTERIOLOGICAL EXAMINATIONS 



be reduced 99.999 percent by this process. The Pasteurization 

 of milk has become an economic problem of great importance in 

 large communities and is not, as it should be, sufficiently super- 

 vised. That method is best in which milk is held at i46F. for 

 thirty minutes. No harm is done to the nutritional value of the 

 milk. One of the dangers of the method is that the commercial 

 Pasteurizing machines are not always thoroughly clean and them- 

 selves contaminate the milk when discharging it after heating. 

 More evidence is on the side of the second view. The practical 

 importance of the controversy is that milk whether heated or not 

 should be kept at a temperature at which bacteria will not mul- 

 tiply, under 6oF. Pasteurized milk is safest in time of typhoid 

 epidemics. 



Absolute cleanliness on the part of the milker, the use of steril- 

 ized gloves and clothes, the absence of flies, dust, and the imme- 

 diate disposal of manure, the nitration of the milk after collection, 

 the immediate cooling of it, the uses of sterilized milk cans and 

 bottles, all lessen the bacterial content of milk. It then keeps 

 better, and is a wholesomer and safer food for infants, especially 

 in hot weather. 



By drinking water containing typhoid bacilli cows cannot 

 be sources of typhoid infection through trie milk. The typhoid 

 bacilli are not transmitted through the bodies and udders of the 

 animals. 



A bacteriologic examination of milk comprises a total count, 

 the presence of colon bacilli, streptococci in pus cells, tubercle 

 bacilli and special species as the case suggests. The first is done 

 as given for water, as is the second. The discovery of streptococci 

 is made by centrifugalizing a definite quantity and examining the 

 sediment for chains, particularly in relation to leucocytes, the pus 

 cells. Tubercle bacilli are found by injecting guinea pigs or by 

 dissolving the milk in antiformin (i part milk and i part 15 per- 

 cent antiformin) warming and examining the sediment after 

 centrifugalization. 



