BACTERIAL CONTENT OF MILK 613 



In New York, Park estimated the average bacterial 

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

 per c.c. in winter and 5,000,000 per c.c. during the hot 

 months. Eyre (loc. 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 formaldehyde. Even in so-called 

 sterilised milks bacteria are rarely completely absent. 



Cream is even richer in bacteria than milk, and averages 

 about 8,000,000, and may contain as many as 30,000,000 

 organisms per c.c. Although all the ordinary species may 

 be met with, milk has a bacterial flora largely its own, 

 comprising many forms producing lactic and butyric acid 

 fermentations. Organisms also occur having more or 

 less specific effects, and giving rise to bitter milk, viscid 

 milk, etc. The lactic ferments are mostly non-sporing, 

 the butyric chiefly sporing, species. The commonest of 

 the lactic ferments are Streptococcus lacticus (non-gas- 

 forming) and B. acidi lactici (gas- forming), which has 

 some similarity to the colon bacillus (see Table, p. 381). 

 Another common lactic organism is the Oldium lactis, a 

 mycelial form, the colonies of which appear as little fluffy 

 tufts. In addition to the organisms named, pathogenic 

 species may be met with viz. the tubercle, diphtheria, 

 typhoid, paratyphoid, Gartner, dysentery, and comma 

 bacilli, the M . melitensis, M. pyogenes, and the Streptococcus 

 pyogenes (lactic-acid-forming streptococci are also common). 

 The B. coli and B. Welchii are generally present in milk, 

 and the B. lactis aerogenes is sometimes found (p. 389). 

 Scarlatina (see " Scarlatina ") and foot-and-mouth disease 

 may likewise be conveyed by milk, and the diarrhoea of 

 infants is largely due to the use of milk swarming with 

 microbes, some of which in themselves may be harmful, 



