470 MICROBIOLOGY OF MILK AND MILK PRODUCTS 



Non-epidemic Diseases. There is another class of diseases which 

 may be carried by milk which are not characterized by a sudden out- 

 break, and for this reason are not so readily recognized as being asso- 

 ciated with the milk supply. One of these diseases, namely tuber- 

 culosis, is caused by the specific, well-known organism, Bad. tuberculo- 

 sis, which may get into the milk from the udder of a tuberculous cow 

 or by the organisms which have been given off from the digestive 

 tract of the animal becoming scattered about the stable and finally 

 getting into the milk with particles of dust and filth. In some 

 cases the milk may become infected by persons having the disease 

 being permitted to handle the milk. Fortunately for mankind Bact. 

 tuberculosis does not multiply in milk. 



Regarding the danger of contracting tuberculosis from the use of 

 milk there is at present some difference of opinion, but the con- 

 sensus of opinion at the present time seems to be that there may 

 not be very great danger for healthy adults, but that a considerable 

 percentage of the cases of tuberculosis of children may be traced from 

 the milk supply. Fortunately none of these specific disease organisms 

 produce spores and the temperatures used in the process of pasteuriza- 

 tion by the ''holding" method are sufficient to destroy any of the dis- 

 ease bacteria known to be carried by milk. 



There is another class of disorders not so well defined as the above 

 but which are nevertheless of great importance from the standpoint of 

 public health, especially of young children and also to some extent of 

 adults. This group includes such disorders as infantile diarrhcea, sum- 

 mer complaint, cholera infantum and other disorders of the digestive 

 tract. The organisms producing these troubles doubtless belong to the 

 group of putrefactive bacteria which come from filth. Some of the gas 

 producers and some of the peptonizers are probably responsible for 

 these troubles. Shiga isolated from a large number of cases of infant 

 diarrhoea a bacterium which he named Bact. dysenteries, but in general 

 the specific organisms responsible for these intestinal troubles are not 

 well known. Their importance, however, is shown by the relation of 

 the germ content of milk to infant mortality (see Fig. 145). 



BACTERIOLOGICAL ANALYSIS OF MILK 



The development of our knowledge of the relation of bacteria to the 

 wholesomeness of foods has led to a study of the bacterial content of 

 milk as a means of determining its purity. The methods used for this 

 purpose have followed quite closely those of the water bacteriologists. 



