THE NATURE OF BACTERIA. IQ 



because some of them are poisonous is manifestly illogical ; 

 but this is exactly what has been done in regard to bacteria. 

 The more they have been studied the more evident has it become 

 that they perform other important functions in nature besides 

 that of producing disease ; that, indeed, the production of dis- 

 ease is really only a comparatively rare property, possessed 

 by a few of the numerous species of this group of organisms. 

 As bacteriologists have widened their views and looked outside 

 of the human body they have found that these organisms are 

 not only excessively abundant in nature, but that they play a 

 part in the phenomena of living things which has been wholly 

 unexpected. As far back as 1860 Pasteur had shown their 

 agency in the souring of milk, and within the last twenty years 

 a larger and larger amount of attention has been directed to 

 the part played in nature by those species of bacteria which 

 have no relation to human disease and are never parasitic. As 

 a result there has developed a new branch of bacteriology 

 which deals with phenomena wholly separate from disease. 



In particular we have learned 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 w r hich are going on in 

 the soil, water and elsewhere, and which are essential to agri- 

 culture. 



Agricultural bacteriology is to-day the advance ground of 

 research. It is only about two decades since our scientists 

 have seen the importance and the greatness of the field, and, 

 although the advance in this short period of time has been 

 rapid, it is inevitable that many problems should be still un- 

 settled. While we have studied, in considerable detail, many 

 of the phenomena where bacteria are concerned in agricultural 

 processes, it is not to be expected that the few years during 

 which the subject has been under investigation shall have done 



