WHAT ARE MICROORGANISMS? 5 



largely adopted all over the world; but they have generally been 

 adopted by farmers in ignorance that they are benefiting from 

 bacteriological research. That these practical applications of 

 bacteriology to agricultural processes will increase with the next 

 few years is certain. Successful agriculture of the future is in- 

 dissolubly bound up in the problem of the proper handling of 

 microorganisms. We have reached a point where every advanced 

 farmer, who wishes to put himself into a proper condition to make 

 the best use of the means at his disposal and to profit by discoveries 

 as they are made, must at least have a general knowledge of the 

 fundamental factors of bacteriology as they are related to agriculture. 



WHAT ARE MICROORGANISMS? 



In studying the relation of germ life to the farm we are concerned 

 with a class of phenomena called fermentation, putrefaction, decay, 

 decomposition, and the like (see Chapter II). These phenomena 

 are all caused by living bodies that are frequently called microorgan- 

 isms. This term strictly means animals or plants of microscopic 

 size. But this conception of the term is at once too narrow and too 

 broad to cover the organisms we are to study. Some microscopic 

 organisms have no particular relation to the classes of phenomena 

 which we are considering. A great host of microscopic, green 

 water-plants and also many microscopic animals have nothing to do 

 with our subject, though they might properly be called micro- 

 organisms. On the other hand, some plants of large size, like molds 

 and toadstools, have a part to play in producing the decomposition 

 of organic structures very similar to that played by bacteria. These 

 cannot properly be called microorganisms, but nevertheless they 

 must be included with the study of bacteria and yeasts, since they 

 perform similar or closely allied functions in nature. A better term 

 to cover the organisms which we must study might be the rather 

 broad term of Fungi, for all of the organisms with which we are 

 concerned belong to this general class of plants. But this term is 

 also unsatisfactory, since it fails to convey the idea that the organisms 

 are largely microscopic. To most people the term fungus gives at 



