430 



MICROBIOLOGY OF MILK AND MILK PRODUCTS 



COMMON MILK. When we recognize the extreme ease with which 

 milk undergoes bacterial changes, we are not surprised to find that 

 ordinary milk, when delivered to the consumer, contains relatively 

 large numbers of bacteria. Age is one of the chief factors in de- 

 termining the germ content of milk. We, therefore, expect to find 

 the milk in large cities having a much higher germ content than in 

 smaller cities and towns. The normal germ content of ordinary 

 milk as it is found in the cities may be shown by the following 

 tables. 



BACTERIA IN BOSTON MILK* 



Average taken from 2,394 Samples 



From June to September 



Per cent 

 Below 100,000 bacteria per c.c 42.0 



Between 100,000 and 500,000 per c.c 29. 75 



Between 500,000 and 1,000,000 per c.c 9-75 



Between 1,000,000 and 5,000,000 per c.c 12.75 



Above 5,000,000 per c.c 5.0 



Uncountable plates 0.75 



BACTERIAL COUNTS OF CHICAGO (RAW) 



Date Number of Average Lowest Highest 



samples count count count 



January 64 1,067,000 27,000 5,500,000 



April 43 5,948,000 14,000 150,000,000 



July 183 12,548,000 8,000 190,000,000 



BACTERIA IN MILK OF CONNECTICUT CITIES J 



Bacterial count Number of samples 



Under 50,000 1,707 



50,000-100,000 130 



100,000-500.000 459 



500,000-1,000,000 98 



Over 1,000,000 73 



These figures give the results of 2,467 samples collected in seventy-five different 

 towns in the State covering a period of one entire year. 



Goler gives the average bacterial count for 1,057 samples of market milk collected 

 in Rochester during the year 1909 as 446,099 per c.c. Of these samples 1.79 per cent 

 were above 5,000,000 and 38.4 per cent below 100,000. 



* Data given by Hill and Slack, 

 t Data given by-'Tonney. 

 t Data given by Conn. 



