vi] THE BACTERIA OF MILK 69 



method in which the tubercular bacillus obtains 

 access to the milk there can be no doubt. It does 

 not come into the milk, as a rule, subsequent to 

 milking, but is already in the milk when it leaves 

 the udder. The enormous prevalence of tubercular 

 disease among cows it has been calculated that 2 \ 

 per cent of all cows butchered are infected with 

 tuberculosis renders the danger of milk acting as a 

 propagator of this disease very great. It must not be 

 inferred, of course, that all milk containing tubercular 

 bacilli is equally capable of producing the disease. 

 The probabilities are that where it is present 

 in a sample of milk, this sample, before it is 

 consumed, becomes mixed with a large quantity of 

 milk free from bacilli of this type ; but the resulting 

 dilution, as has been very properly pointed out by 

 Freudenreich, while it diminishes the risk of infection, 

 does not do away with it entirely. Typhus, again, has 

 often been spread by milk. In fifty typhus epidemics 

 which Hart investigated in Engl-and, no less than 

 twenty-eight were found to be due to infected milk. 

 Here, of course, the infection would be imparted to 

 the milk after milking, in any of the many numerous 

 ways in which milk becomes contaminated. With 

 regard to cholera, it has also been proved again and 

 again that milk has been the means of propagating 

 this terrible disease. While lastly, with regard to 

 scarlet fever and diphtheria, Hart has traced no less 



