ILLINOIS STATE DAIRYMEN'S ASSOCIATION. 219 



ble organisms called germs, micro-organisms, or bacteria. Dif- 

 ferent forms of these little creatures produce different effects. 

 Some accomplish useful or harmless changes, while a few, known 

 as pathogenic bacteria, produce disease in their host. If 

 none of them were present no fermentative change would take 

 place. But they are abundant in nature, and manage in some 

 way to get into most organic substances. 



Many persons think of the term bacteria as relating to a dis- 

 ease of some kind; they fail to appreciate that among these 

 micro-organisms man has friends as well as enimies. They are 

 great scavengers, and they have a most important connection 

 with agricultural processes; in manufacturing certain products 

 their action is depended upon almost entirely; they are absolute- 

 ly necessary in the manufacture of fine butter and in giving vari- 

 ety to cheese. 



DESCRIPTION OF BACTERIA. 



Bacteria are so small that it is difficult to form a conception 

 of their size; it would require many hundred of them in a con- 

 tinuous line to extend an inch. A thousand billion of them, if 

 placed together, would weigh but a small part of an ounce. In 

 a single drop of badly infected milk the bacteria may be counted 

 by the million. It is evident that they cannot be seen with the 

 naked eye, but require to be highly magnified in order to be 

 identified. Bacteria are not all of the same size nor the same 

 shape, nor do they all grow alike under the same conditions. 

 Their differences in these respects aid in classifying them. 



They are composed of a single cell, and the most common 

 way by which they reproduce themselves is by the division of 

 the * 'parent" cell into two smaller cells. This is accomplished 

 by the bacterium gradually becoming more and more constricted 

 about the middle until it separates into two parts; these increase 

 in size, and the process is constantly repeated. Under favorable 

 conditions multiplication takes place with great rapidity. A 

 bacterium may develop and be ready to reproduce itself in a few^ 

 minutes. 



