vi] THE BACTERIA OF MILK 103 



that the cholera bacilli may live for four or five days. 

 In cheese, experiments show that they do not seem to 

 be a source of danger. Here again the effect of boiling 

 the milk would be to destroy the cholera germs. 



Typhus Bctcillus. Another pathogenic germ which 

 has been found in milk is that giving rise to typhus 

 (see Fig. 13, p. 77). The number of typhus epi- 

 demics traced to this source has already been referred 

 to. The bacillus of typhus has been found to be 

 able to survive in butter for a period of from five to 

 seven days. 



With regard to the behaviour of other pathogenic 

 germs in milk we know very little. That such 

 diseases as scarlet fever and diphtheria have been 

 propagated by milk we have abundant proof; but as 

 the microbes causing these diseases have not as yet 

 been isolated, we know little about the conditions 

 under which they develop. 



As already pointed out, we have certain moulds 

 and yeasts which frequent milk or milk products. 

 Some of these moulds as, for example, the widely 

 distributed green mould penicillium glaucum (see 

 Fig. 10, p. 73) are familiar in cheese; indeed, 

 the last-named mould plays an important part 

 in the ripening of Eoquefort cheese. It is also 

 familiar in Gruyere, Gorgonzola, and Brie cheeses. 

 Another kind of mould common in milk is the 

 oidium lactis, abundant in sour milk. It presents a 



