106 THE MILK QUESTION 



If all the tuberculosis were eliminated from cattle, or if 

 all the milk in all the world were pasteurized, there would 

 still be an enormous amount of tuberculosis left. In fact, 

 the diminution in the number of deaths from tuberculosis 

 through this one measure alone would be disappointingly 

 small. In other words, the more serious type of tubercul- 

 osis in man is very largely a disease contracted from man. 

 In Japan, for example, where milk is not used at all as an 

 article of diet, there is quite as much tuberculosis as there is 

 in Europe or this country. In the tropics, where practically 

 all the milk is boiled, tuberculosis is very prevalent. It must 

 nevertheless be remembered that the number of deaths 

 and the amount of sickness caused in man from bovine 

 tuberculosis is enormous in the aggregate. 



The tuberculin test. There are several methods of de- 

 tecting tuberculosis in cattle, but the quickest and surest 

 is the tuberculin test. It is a matter of common observation 

 that a cow may be fat and sleek, eat and milk well, have a 

 bright glossy coat, and be apparently in the pink of con- 

 dition, and still be passing tubercle bacilli from an infected 

 udder, or the infection may appear in the faeces as a result 

 of an occasional cough. As a matter of fact, milch cows, 

 during a certain stage of tuberculosis, often furnish a large 

 yield of milk. 



Before tuberculosis can be eliminated, it must first be 

 detected. There are two methods by which the disease 

 may be diagnosed. One is through physical examination 

 and the other by the tuberculin test. Compared with each 

 other the diagnosis by physical examination is crude, 

 unsatisfactory, and inaccurate, while the diagnosis with 

 tuberculin is refined, delicate, and precise. 



The substance known as tuberculin was discovered by 

 Koch in 1890. Tuberculin is made by growing a pure cul- 

 ture of tubercle bacilli in bouillon, which is then sterilized 

 by heat and the dead bacilli filtered out. Koch 's tuber- 

 culin, therefore, does not contain the bacilli themselves, 



