WHAT ARE MICROORGANISMS 5 
many questions remain unsolved. Scientific discovery usually 
precedes any practical application, and in these early years of 
the development of agricultural bacteriology we must expect to 
find the theoretical side of the subject proceeding rapidly, while 
the application of the facts to farm methods lags behind and is, 
in many respects, hesitating, tentative, or even unsatisfactory. 
Nevertheless, the discoveries made have already revolutionized 
agricultural processes. Changes in agricultural methods, due to 
bacteriology, have been 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 agri- 
culture of the future is indissolubly bound up in the problem of 
the proper handling of microdrganisms. 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 con- 
cerned with a class of phenomena called fermentation, putrefac- 
tion, decay, decomposition, and the like (see Chapter IT). These 
phenomena are all caused by living bodies that are frequently 
called microdrganisms. 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 micro- 
scopic animals have nothing to do with our subject, though they 
