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 
TxuroucH 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’ examined 233 samples in 
Washington in 1906 and found tubercle bacilli'in 6.72 
1U.S. Hygienic Lab. Bull., No. 56, pp. 167-197. 
