224 ILLINOIS STATE DAIRYMEN'S ASSOCIATION. 



marked influence on the bacterial content. He examined the 

 milk of a patron on two successive days, the iirst being warm 

 and the second cold and rainy; i cubic centimeter contained, re- 

 spectively, 1,150,000 and 48,000 bacteria, or about one twenty- 

 fifth as many on the cold, wet day as on the warm day. It is 

 apparent that this difference was due chiefly to the purity of the 

 atmosphere and a lower temperature. 



Another investigator counted from 50,000 to 100,000 germs 

 per cubic centimeter of the first milk drawn. In some cases 

 the last milk is sterile, or germ free; in others it contains numer- 

 ous germs. City milk usually contains from 10,000 to hundreds 

 of thousands of bacteria in a single cubic centimeter. 



The number of bacteria in a sample of milk is an indication 

 of its purity, but not an absolute proof that it is or is not of 

 good quality. Large numbers of harmless bacteria are some- 

 times found in good milk. It is the harmful ones and those 

 that are liable to become harmful if present in too large num- 

 bers, that chiefly concern the dairyman. If they are kept out 

 of the milk, or their growth is controlled, the number of harm- 

 less ones will also probably be reduced, for the measures that 

 restrict one class have a like effect on the other. Whenever 

 large numbers of harmless germs are found there is probability 

 that dangerous forms are included. 



KINDS OF DAIRY BACTERIA. 



Over 200 different kinds of dairy bacteria are found in milk 

 and its products, new and old. Many of these have not been 

 completely described and will require much more study before 

 their characteristics are fully understood. Different forms are 

 found in different sections of the country. Different sources of 

 contamination contribute different types of bacteria to the milk, 

 and the large number of forms does not seem strange when their 

 many sources are studied. One would expect to find a differ- 

 ence in kinds as well as in numbers of bacteria in milk of cows 

 kept in pasture and milked in the open air, and in milk of cows 

 continuously stabled. Such is the case. Especially is this true 



