INFLUENCE OF DISEASE UPON MILK 73 



occurs in the non-tuberculous forms of mastitis, they 

 are, of course, always eliminated in the milk. 



In considering the influence of disease of the cow on 

 market milk, the effect of dilution must not be overlooked. 

 Milk from a diseased cow may be injurious when ingested 

 by itself, but when it is mixed with the milk from a num- 

 ber of other cows in a normal condition it may be 

 so diluted as to render it harmless. The character of the 

 mixed milk in this respect will depend partly upon the 

 proportion of diseased cows to those in health, partly 

 upon the ability of the organism concerned to grow in 

 milk, and the temperature at which the milk is kept. 



The diseased conditions affecting milch cows which 

 are of importance in milk hygiene will now be considered 

 separately. 



I. DISEASES or CATTLE TRANSMISSIBLE TO MAN 

 THROUGH MILK 



TUBERCULOSIS 



In milk hygiene there are four points to be considered 

 in connection with tuberculosis: (1) The frequency of 

 tubercle bacilli in market milk, (2) the virulence for 

 man of tubercle bacilli from cattle, (3) the conditions 

 under which milk is infected with tubercle bacilli by 

 tuberculous cows, and (4) how can contamination of 

 market milk with tubercle bacilli be prevented. 



1. The Frequency of Tubercle Bacilli in Market Milk. 

 In a number of cities in this country and abroad, samples 

 of market milk have been collected and examined for 

 tubercle bacilli. Anderson 1 examined 233 samples in 

 Washington in 1906 and found tubercle bacilli in 6.72 



1 U. S. Hygienic Lab. Bull., No. 56, pp. 167-197. 



