DISEASE GERMS IN MILK gi 



after which for considerable time she may produce infected 

 milk without there being any visible indication that the udder 

 |ias been affected. The only logical conclusion to be drawn is 

 that any animal suffering from the disease is a source of 

 danger, inasmuch as we cannot tell when she may begin to 

 produce infected milk. At the same time, we must recognize 

 that only a small proportion of the animals actually suffering 

 from tuberculosis produce infected milk, although we have no 

 means of knowing how large the proportion is. It is a matter of 

 more practical importance to learn whether market milk is 

 actually infected. A microscopic study of market milk and 

 market butter has demonstrated beyond peradventure that the 

 milk sold to the public is more or less frequently infected 

 with the tuberculosis bacillus from animals. Here, again, per- 

 centages are quite impossible, because of the difficulty of the 

 tests and the lack of a sufficient number of experiments. 



One very important phase of the relation of this disease to 

 milk distribution should be emphasized and clearly understood. 

 The tuberculosis bacillus does not multiply in milk. This germ 

 will not grow at all, unless the temperature is kept close to body 

 heat, and it does not develop outside of the human body by 

 any known natural media. The germs which pass from the 

 cow into the milk will remain alive therein for a considerable 

 length of time and are, perhaps, capable of doing injury; but 

 they do not increase in numbers. Hence, it follows that the 

 general mixing of milk before it reaches market is quite sure 

 to distribute the germs somewhat widely in the different por- 

 tions of the milk, and this dilution greatly decreases the number 

 in any particular sample of milk. 1 Inasmuch as the germs do 

 not grow, the more the infected milk is diluted with uninfected 

 milk the more the germs will be reduced in numbers in each 

 sample. 



A second factor of no less importance is that if these germs 



1 Gebhardt. Virch. Arch., p. 119, 1890. 



