Bacteriology and Its Significance 37 



While this was the practice in those remote times, it was only 

 within very recent years that anything- like the true significance of 

 these basic agricultural principles have been discovered. Indeed soil 

 microbiology is far from being understood even today. 



We now know that there are (a) bacteria which are normal in- 

 habitants of the soil which render the organic matter (humus) in such 

 form that it is available to the growing plant. These "rotting bacteria" 

 disintegrate the dead plants and animals forming ammonia and other 

 compounds. It was commonly supposed that the nitrogen of the air 

 was worthless unless changed to ammonia by electric storms or similar 

 disturbances. There are (b) bacteria (azotobacter, Clostridium) which 

 grow in the soil as well as (c) those that live in symbiotic relationship 

 (radicicola) and are found in the nodules (bacteroides) on the roots 

 of certain plants (legumes) all of which have the property of changing 

 atmospheric nitrogen into an assimilable form for the growing plant. 

 Modern scientific agriculture which results in the increase of soil pro- 

 ductiveness must necessarily embody and encourage the growth of these 

 groups of helpful bacteria which elaborate chemical compounds re- 

 quired for proper development of the crop plant and discourage harmful 

 forms of which there are also many. 



Proper effective sanitary and public health methods become neces- 

 sary in view of the fact that the soil harbors, in addition to those that 

 are harmful to lower plants and animals, certain organisms that are 

 pathogenic to higher animals including man, causing diseases such as 

 lock-jaw, tuberculosis, typhoid fever, gangrene, anthrax, foot and mouth 

 disease, lumpy jaw, hook worm and other intestinal parasitic infections. 

 In certain parts of the country proper drainage and tillage of the soil 

 have proven to be very beneficial by removing, as much as possible, 

 the breeding places of mosquitoes which carry malaria and yellow fever. 



The selection of a pure water supply and the proper disposal of 

 sewage is of the greatest importance in the conservation of public 

 health. A pure water supply is especially essential in the prevention 

 of such diseases as typhoid fever, dysentery and cholera. 



The extermination of pests such as chinch bug, rats, mice, rabbits 

 and squirrels by means of microbes is at present apparently not entirely 

 successful from a practical standpoint. It has, however, possibilities. 



In the development of bacteriology the relation of bacteria to dis- 

 ease undoubtedly received the greatest prominence. Especially was 

 this true because, with the discovery of the microscope, bold scientists 

 often unhestitatingly declared that they had seen the germs causing 

 such diseases as plague^ syphilis and smallpox. 



The germ theory of disease of Kircher of over two hundred years 

 ago, coupled with van Leeuwenhock's observations and finally brought 

 to a crowning climax through the works of Pasteur and Koch, is a 

 thing of the past. Micro-organisms, as has been demonstrated thousands 

 of times, are responsible for a great number of infectious diseases. 

 This positively proven fact is unquestionably an important one and of 

 even greater significance are the results which aid us to scientifically 

 and successfully prevent and combat these diseases. 



