20 ILLINOIS DAIRYMEN'S ASSOCIATION. 



tion of milk. I hardly need say to a dairy audience that the production of 

 wholesome milk is a necessary thing in first-class dairy productions. 



Until, a few years ago the feeding of animals for the production of 

 milk was not the important factor, but within the last ten or fifteen years 

 there has come into dairying a literally new factor. It is, of course, a fac- 

 tor that has been operative from time immemorial, but we have only begun 

 to appreciate that the quality of milk was dependent upon the presence 

 or absence of certain living organisms. These organisms are what is 

 known as bacteria, and the science which treated of these living organisms 

 was relatively a new science. It is a science, however, which is most 

 intimately related to dairying, and the importance of this is becoming 

 more and more appreciated. 



The word bacteria recalls in the mind a vision of diseases. We hear 

 so much about microbes and bacteria of this and that, that we look upon 

 these organisms as being the agents in the production of disease. Some 

 of them are agents of this sort, but the great bulk of bacteria belong to 

 an entirely different class. Some of themi are even beneficial, and a great 

 many of them are indifferent to us as human beings. In this class of liv- 

 ing organisms we are dealing with something which is alike capable of 

 growth, and the same conditions which are necessary for the growth and 

 development of ourselves, are to plants likewise necessary for the growth 

 of these bacteria species. They must have light, proper temperature, the 

 proper food supply, the same as is necessary for all kinds of living things. 



A recollection of this fact is of importance because it teaches us that 

 we have in milk the conditions which are more suitable for the growth of 

 this type. It is strange that we have here a common meeting ground of 

 the highest and lowest forms of existence known. 



Milk, as you know, is that substance which is designated by nature 

 for nourishment of the young. 



Now the changes which take place in milk are changes which are 

 conditioned upon the presence or absence of this type of germ life. We 

 have the souring of milk, the transfer of milk into the slimy or ropey 

 milk, bitter milk, etc., which are some of the changes and which are wont 

 to bother the dairyman. 



It is only recently, within the last few decades, that an explanation 

 of the cause of these changes has become apparent, or has become 



