14 THE MODERN MILK PROBLEM 



which tend to make the milk an unfit or deleterious 

 food. 



The extent of such bacterial changes in milk from the 

 time that it is drawn from the cow to the time it reaches 

 the consumer depends upon three things: (1) the 

 kinds and amounts of contamination, (2) the tempera- 

 ture of the milk, and (3) the time in transit. The con- 

 tamination can be reduced to a minimum, the tempera- 

 ture can be kept low, and, if these two conditions are 

 right, a reasonable time in transit can be allowed. 

 Under practical circumstances some latitude must be 

 permitted in the endeavor to approach the ideal, 

 namely, that milk should be clean, fresh, and cold. 



2. Infection. A different case is that of infection. 

 The germs of various diseases may gain access to milk, 

 in which they live and frequently multiply. This is 

 not merely a matter of contamination but of the trans- 

 ference of the secretions of already infected animals or 

 persons. Relatively small contamination may in this 

 case result in virulent and far-spreading specific infec- 

 tion. The unwashed hands of milker or milk-handler 

 in an unrecognized stage of disease, infected manure 

 from tuberculous cows, utensils which have been in- 

 fected by washing in polluted water or in some other 

 way: such are typical modes of infection. Polluted 

 milk may at any time prove to be infected milk; it is, 

 so to speak, a lottery of infection. Infection is pos- 

 sible even with a high degree of visible cleanliness, for 

 infected individuals may be unrecognized and the trans- 

 ference of infectious matter undetected. Milk-borne 

 disease, like other infection, "walketh in darkness." 



Special reference must be made to carriers of com- 



