MICROORGANISMS AND FARM LIFE. 3 
disease. Their relation to the medical profession was soon 
recognized, and more or less extended courses in bacteriology have 
rapidly made their appearance in medical schools. Health boards 
and sanitary officers have recognized that their primary duty is 
to deal with bacteria; and most of the regulations for the preserva- 
tion of the public health have been directed toward the destruction 
or control of these organisms. 
As more information has accumulated during the last twenty 
years or so, it has become evident that microorganisms, including 
bacteria, do not deserve all the ill repute that they have acquired. 
It has been learned that there are hundreds and even thousands of 
kinds of bacteria, and that, while certain species are the cause of 
disease, others are harmless, some are beneficial in the body, and 
many perform functions of the highest significance and value. 
Although the disease side of the bacteria story was the first to be 
studied, it is only a small part of the subject. Among the many 
hundred kinds of bacteria known, only a few, less than two score, 
are as yet definitely known to have any power of causing disease 
in man. As bacteriologists have widened their views and looked 
outside of the human body, they have found that these organ- 
isms are not only excessively abundant in nature, but have 
relations to the phenomena of living things which were wholly 
unsuspected. Within the last twenty years a larger and larger 
amount of attention has been directed to the part played in nature 
by microorganisms which are never parasitic and have no relations 
to human disease. As a result there has developed a new branch of 
bacteriology which deals with phenomena wholly separate from 
disease. 
Relation to Agriculture. In particular it has been shown 
that bacteria are related to agriculture. Not only is it true that 
they are the cause of certain animal and plant diseases with which 
the farmer has to contend, but it is becoming manifest that they are 
intimately associated with many normal processes which are going 
on in the soil, water, and elsewhere, and that they are fundamental 
to the processes of agriculture. 
The agricultural side of bacteriology is, if possible, more impor- 
