612 A MANUAL OF BACTERIOLOGY 



Milk 1 



Milk is an admirable nutrient soil for the development 

 and multiplication of micro-organisms, and, though sterile 

 in the udder, 2 as delivered to the consumer may contain 

 an appalling number of bacteria. In milk as ordinarily 

 supplied there are from one to five million bacteria per c.c., 

 and it frequently contains ten to fifteen 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 railway 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 

 present rapidly multiply in warm weather. Eyre 3 in 

 the middle of summer found the following rate of multi- 

 plication : 



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 



1 See Houston, Rep. to the London County Council, No. 933, 1905 ; 

 MacConkey, Journ. of Hygiene, vol. v, 1905, p. 333 ; Hewlett and 

 Barton, ibid. vol. vii, 1907, p. 22 ; Savage, Rep. Med. Off. Loc. Gov. 

 Board for 1909-10, p. 474, and Milk and the Public Health (Macmillan, 

 1912) ; Swithenbank and Newman, Bacteriology of Milk. 



2 The " fore " milk may contain organisms which have lodged in the 

 milk-ducts, and it is extremely difficult to obtain completely sterile milk. 



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



