214 AGRICULTURAL BACTERIOLOGY. 



occur on the farm, that it is hardly a matter of significance to 

 agriculture. 



Diarrhceal Diseases. Besides the diseases mentioned the 

 only others of importance commonly distributed by milk form 

 that somewhat obscure class of diseases characterized by 

 diarrhceal troubles, especially prevalent in warm weather. Of 

 these by far the most serious is cholera iufantiim which is re- 

 sponsible for the death of so many children. These troubles 

 are less understood than most bacterial diseases. They do 

 not appear to be caused by any single specific bacterium, but 

 are probably due to the excessive multiplication of a number 

 of different bacteria in the milk. That they are due to the 

 milk bacteria is proved by the fact that they occur in greatest 

 abundance at the seasons of the year when milk bacteria arc 

 most numerous, that they are chiefly confined to infants fed 

 upon cow's milk, and lastly, by the fact that they become 

 greatly reduced in numbers when the custom of sterilizing or 

 pasteurizing milk is adopted. What kind of bacteria are at 

 fault in the production of these diseases we do not know. 

 Quite a number of bacteria are found in milk which produce 

 poisonous secretions and which may be agents in the produc- 

 tion of these obscure diseases. For the purpose of our dis- 

 cussion it is sufficient to state that they are probably to be 

 regarded as the bacteria of filtli, and that anything which in- 

 creases the amount of filth in the milk will have a tendency to 

 increase the amount of such troubles, while any advance in 

 cleanliness will have an influence in the opposite direction. 



From all these reasons it is evident that it is of the greatest 

 importance, both to the farmer and the public at large that : 

 (i) The number of bacteria in milk should be kept as low as 

 possible ; (2) the greatest care should be exercised to prevent 

 secondary contamination of milk with typhoid bacilli, either 

 through water or by contact with infected persons ; (3) per- 

 sons suffering or recovering from scarlet fever or diphtheria 



