TUBERCULOSIS. 377 



It is true that the bacilli do not multiply in milk, but milk 

 from one cow can, by being mixed with other milk, infect a 

 large amount. It is possible that such milk may be a danger to 

 the public health. Nor does this conclusion rest simply upon 

 theory, for there is direct evidence to support it. Several 

 instances, not very numerous, naturally, from the difficulty of 

 obtaining evidence, are on record where mankind has been 

 said to have acquired the disease from drinking milk of infected 

 animals. It has been abundantly shown that market milk 

 frequently contains tubercle bacilli in sufficient quantity to 

 produce an infection in guinea-pigs, and the same is true of 

 market butter. All of these facts certainly indicate a possible 

 danger to the public from this source. 



In regard to the extent of this danger there has been a wide 

 difference of opinion. It has certainly been magnified by some. 

 The danger is, beyond question, frequently overdrawn. That 

 mankind can ever acquire tuberculosis from this source is to- 

 day seriously questioned. It must be remembered that milk 

 is taken directly into the stomach, and if it gives rise to tuber- 

 culosis it would be expected that the seat of the disease would 

 be in the intestinal tract. It is, however, well known that in 

 mankind the lungs are the most common seat of infection, and 

 we can hardly believe that drinking milk would be the likely 

 cause of pulmonary tuberculosis. Moreover, the number of 

 bacilli which a person will swallow with a drink of milk will 

 commonly be rather small, and the human individual has a 

 considerable power of resistance against the disease. It is a 

 further fact that, although bovine tuberculosis has been in- 

 creasing, human tuberculosis has been constantly declining in 

 recent years, and the decline has been equally great in those 

 countries that use milk raw and in those countries that sterilize 

 the milk before drinking it. This decrease in tuberculosis does 

 not apply to intestinal tuberculosis among young children, indi- 

 cating, possibly, that milk is a more common source of infection 

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