226 ILLINOIS STATE DAIRYMEN'S ASSOCIATION. 



example, a species which causes bitter milk does not thrive until 

 the ordinary sour milk (lactic acid) germs have developed some 

 acidity. 



It is not necessary to go into details as to the many different 

 changes produced directly and indirectly by numerour forms. 

 Some are troublesome whenever they find their way into the 

 milk, others become a nuisance only when they are present in 

 very large numbers. Types that color the milk, form gas, or 

 produce disagreeable flavors are always objectionable. 



Farmers' Bulletin No. 29 treats more fully aud technically 

 of the bacterial changes of milk. The bad effects of those bac- 

 teria which produce a pronounced change in milk are usually 

 confined to the milk itself. Its change is so marked that it is 

 rarely used as food. 



Some bacteria thrive in milk and do not have a marked effect 

 on it but may cause disastrous results to the consumer. These 

 are germs of disease and should be most carefully guarded 

 -against. Good proof exists of the transmission of several dis- 

 eases by milk, and in a number of instances epidemics have been 

 traced to an infected milk supply. 



Another kind of bacterial action which may indirectly result 

 in injury to health is referred to by Conn. He states that some 

 of the common milk bacteria may be present in such great num- 

 bers as to produce poisonous toxins "which are directly injurious 

 to the weak stomach of the infant or of the invalid." Many cases 

 of cholera infantum and similar troubles are said to be due to 

 these causes. 



All forms of bacteria are objectionable in milk that is to be 

 consumed as food in its natural state, and, indeed, most forms 

 are undesirable in milk that is to be manufactured. 



HOW TO KEEP MILK PURE. 



Experiments have shown that the contamination of milk oc^ 

 curring under ordinary circumstances can be reduced over 95 

 per cent by taking care to avoid all possible sources of impurity 

 ,and conditions favoring germ growth. The fact that bacteria 



