CHAPTER I 



WHAT ARE BACTERIA? 



BACTERIA were first seen two centuries ago by a Dutch micro- 

 scopist, Leeuwenhoek, but were mostly forgotten for the century 

 following. About 65 years ago it was first seriously suggested 

 that these minute organisms might be of some significance in 

 nature, and even at that time one unusual phenomenon of the 

 dairy blue milk was attributed to the action of microscopic 

 germs. About 1860 Pasteur showed a close connection be- 

 tween microscopic life and the souring of milk; but it was not 

 until about 18 years ago that they were conceived to have a 

 very intimate relation to dairying. 



Dairy Bacteriology has practically all developed in the last 

 two decades. The advance has been extremely rapid, and it is 

 not an exaggeration to say that in this brief time bacteriology 

 has revolutionized all dairy methods, from the cow to the con- 

 sumer's table. The dairyman of to-day, and even more the 

 dairyman of to-morrow, must understand bacteriology both 

 theoretically and practically. 



THE MICROSCOPIC APPEARANCE OF BACTERIA 



The dairyman who is trying to do any practical work with 

 bacteria in his dairy business does not ordinarily need to use 

 a microscope. The organisms are so small that they must al- 

 ways be handled in masses, and for this purpose, though a 

 microscope is extremely desirable, it is not absolutely necessary. 

 The dairyman has rarely time to^use a microscope properly. 

 The student, however, who is learning of the bacteria in milk 

 and their properties, must make a careful microscopic study. 



