70 Dairy Bacteriology. 



fected animal becomes a positive menace to the herd. 

 As the time when the lesions change from the ' ' closed ' ' 

 to the "open 7 ' type and the animal becomes a source 

 of danger cannot be determined, the only safe way to 

 do is to exclude the milk of all tuberculous animals 

 from the general supply, whether for direct consump- 

 tion, or for manufacture into dairy products and to 

 look upon every diseased animal as a menace to the 

 herd. This is rendered all the more necessary when 

 the milk is used for the feeding of children, who are 

 relatively more susceptible to intestinal infection than 

 the adult. The early stages of the disease in cattle are, 

 however, so insidious that no reliance can be placed 

 upon the detection of the malady by physical means. 

 Fortunately, in the tuberculin test, a method is at hand, 

 which in a simple, but effective manner, enables the 

 disease to be distinguished in even the early stages, 

 long before recognition is possible in any other way. 



Tubercle bacilli in dairy products. When infected 

 milk is used for the preparation of butter and cheese, 

 the organisms inevitably are incorporated in them. In 

 the separation of milk a relatively large part of the 

 tubercle organisms in the milk appear in the cream. 

 In the making of cheese even more of the organisms are 

 held in the curd. In butter and cheese, as in milk, no 

 growth of the organism can take place; however, the 

 vitality of the organism is retained for a considerable 

 number of months. It is not believed that these prod- 

 ucts are of much importance in the spread of tubercu- 

 losis in the human family, since they are not consumed 

 by children to any extent. Cream is to be considered 

 as a means of distribution since it is often used by 

 children. 



