THE RELATION OF MICROORGANISMS TO MILK. 329 



Injurious Organisms. The diseases which may be carried by milk 

 are of two classes. 



Epidemic Diseases. The human diseases most commonly carried 

 by milk are typhoid fever, diphtheria and scarlet fever and occasionally 

 other diseases such as cholera and foot-and-mouth disease. The first 

 three are by far the most important of milk-borne diseases. The 

 outbreaks of typhoid fever which are traceable to milk occur most fre- 

 quently. There is a large accumulation of data showing the occurrence 

 of epidemics caused by infected milk. An epidemic caused by the milk 

 supply has certain characteristics which distinguish it from epidemics 

 resulting from other causes. A considerable number of cases of the 

 particular disease will appear almost simultaneously and will be dis- 

 tributed along some particular milk route. Usually the epidemic stops 

 as suddenly as it began except for a few secondary cases contracted from 

 those first taken. The source of the disease organisms is a human 

 patient suffering from the disease. The infection of the milk may be 

 direct, as when a sick person handles the milk, or it may be indirect as 

 when a person caring for a patient also works about the milk. In other 

 cases it may be caused by contamination of the water used in washing the 

 utensils or by cows wading in water of infected streams and getting the 

 organisms on their body whence they fall into the milk pail at milk- 

 ing time. Unfortunately the specific organisms of these diseases grow 

 readily in milk and a small infection is all that is necessary to render the 

 milk dangerous by the time it reaches the consumer. The return of 

 milk bottles from the sick room sometimes is the means of infecting the 

 milk supply. 



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

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

 outbreak, and for this reason are not so readily recognized as being 

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

 culosis, is caused by a specific, well-known organism, Bact. tuberculosis, 

 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 



