Infection of Milk. 71 



Treatment of tuberculous milk. It is easily possible 

 to treat milk or factory by-products so as to render 

 them positively safe. The process of pasteurization or 

 sterilization is applicable to whole milk, and when ef- 

 fectively done destroys entirely the vitality of any 

 tubercle bacilli. In making such exposure, care should 

 be taken to prevent the formation of the "scalded 

 layer," as the resistance of the organism toward heat 

 is greatly increased under these conditions. In a closed 

 receptacle, 140 F. for 15 to 20 minutes has been found 

 thoroughly effective in destroying this organism. A 

 momentary exposure at 176 F. is likewise sufficient. 

 This is the method that is almost universally used in 

 Denmark in the manufacture of the finest butter. 



In the treatment of factory by-products, heat should 

 also be employed. In Denmark, compulsory pasteuriza- 

 tion at not less than 176 F. is required. This treat- 

 ment prevents not only the dissemination of tubercu- 

 losis among hogs and young cattle, but is equally ef- 

 ficacious in preventing the spread of foot and mouth 

 disease. 



The per cent of tuberculous milch cows varies widely 

 in different sections of the country, being greatest in 

 the older dairy sections, and in those supplying milk 

 to the cities, on account of the constant buying and sell- 

 ing of animals, thus giving more frequent opportunity 

 of introducing the disease into the herds. Throughout 

 the country at large, probably less than ten per cent 

 of the cows are tuberculous, and it is estimated that 

 at least one per cent of the diseased animals have tuber- 

 culous udders. It has been suggested that the dilution 

 of the milk of such animals with that of healthy cows 

 would remove a great part of the danger from milk. 



