BACTERIOLOGY OF MILK 737 



millions, with an average of about three to four millions. 

 Hewlett and Barton found an average bacterial content 

 of about 1,500,000 in London milk as delivered at the rail- 

 way termini (the range was from a minimum of 20,000 to 

 a maximum of 8,390,000), but this does not represent the 

 condition of the milk as delivered to the consumer, for the 

 bacteria already present rapidly multiply in warm weather. 

 Eyre l in the middle of summer found the following rate 

 of multiplication : 



Microbes per c.c. 



Initial content . . . 56,000 



After 12 hours . . . 526,000 



After 24 hours . . . 20,366,000 



After 30 hours . . . clotted 



A similar specimen in the middle of winter gave the 



following results : 



Microbes per c.c. 



Initial content . . . 20,000 



After 12 hours . . . 24,000 



After 24 hours . . . 43,000 



After 30 hours . . . 280,000 



In New York, Park estimated the average bacterial 

 content of milk as supplied to the consumer at 1,000,000 

 per cubic centimetre in winter and 5,000,000 per cubic 

 centimetre during the hot months. Eyre (foe. cit.) states 

 that, as the result of his observations, the numbers are 

 in London about 3,000,000 to 5,000,000 in December, 

 January, and February, and 20,000,000 to 30,000,000 in 

 June to September, smaller numbers than these always 

 being associated with the presence of boric acid or form- 

 aldehyde. Even in so-called sterilised milks bacteria 

 are rarely completely absent. 



Cream is even richer in bacteria than milk, and averages 



1 Journal of State Medicine, vol. xii, 1904, p. 728. 

 M.B. 47 



