26 MILK AND THE PUBLIC HEALTH ch. n 



tamination in the retailer's premises. As Orr, however, is 

 careful to point out, the number of experiments is small and 

 the results are chiefly of value for comparative purposes. 



In a similar way Orr adopted the plan of taking control 

 samples to determine the actual contamination in the con- 

 sumer's house, the controls being kept at the same temperature 

 and for the same time as the consumer's own milk. The 

 samples were from all classes of houses, " from the small 

 through-house in slum districts to the self-contained house." 

 Twenty-six such control experiments were carried out. In 1 9 

 cases the samples from the consumer's own milk showed an 

 increase over the controls varying from I'l to 170' 9 per cent. 

 In 7 cases there was a decrease varying from 1'4 to 4 5 '6 per 

 cent. The average time in the house was 8 hours. The 

 average increase was 2 3 '5 per cent, which Orr takes as the 

 contamination in the consumer's house. 



In these particular experiments the cleanliness of the 

 house did not apparently materially affect the bacterial content 

 of the samples. It should, however, be pointed out that flies 

 were not prevalent to any marked extent during the time 

 these experiments were made. 



The important part played by flies in transmitting specific 

 infection is being increasingly recognised. By feeding upon 

 excreta and decomposing matters and then upon milk, sugar, 

 and other foods flies probably frequently act as the actual 

 vehicle of transmission of the specific disease - producing 

 bacteria. The typhoid bacillus has been isolated from flies. 



