572 MANUAL OF MILK PRODUCTS 



produced by the growth of bacteria on the surface of the cheese, 

 while in such cheeses as the Camembert, the curd is ripened 

 by the enzymes produced by the growth of the white mold on 

 the surface, while the flavor is due to the combined action of 

 the lactic acid bacteria and oidium lactis. 

 Disease organisms in cheese. 



But little work has been done regarding the presence of dis- 

 ease bacteria in market cheese. Harrison 1 conducted a series 

 of experiments to determine the length of time the tubercle 

 bacilli would persist in cheddar cheese. He made a series of 

 cheeses from milk specially inoculated with cultures of tubercle 

 bacilli, which were tested at intervals by inoculation experi- 

 ments with small animals. As a result of his experiments, he 

 concludes as follows : 



"If cheddar cheese as commonly made in the United States 

 and Canada happens to contain tubercle bacilli naturally 

 present, it may be assumed that none of these germs will be 

 living when the cheese becomes ten weeks old. Hence, no 

 danger need be apprehended of acquiring the disease known as 

 consumption by eating well-cured cheddar cheese." 



Mahler, Washburn, and Doane, 2 after reviewing the experi- 

 mental work on this subject, draw the following conclusions : 



"As a result of these various experiments it is evident that 

 the bacillus of tuberculosis not only retains its life but also its 

 virulence in cheese for a considerable period in time, and that 

 cheese made from raw, unpasteurized milk should therefore 

 be considered as a possible carrier of tubercle bacilli. 



"Knowing that there are many tuberculous cows among the 

 dairy herds which furnish milk for the manufacture of cheese 

 in this country, it is evident that some steps should be taken 

 to prevent the introduction of living, virulent tubercle bacilli 

 into this important food product. The best possible means to 



1 Annual Report Bureau Animal Industry, 1902. 



2 Annual Report Bureau Animal Industry, 1909. 



