Bacteria and Agriculture 



11 



resistance possessed by animals, of natural and acquired 

 immunity to disease, and of the methods whereby im- 

 munitj^ may be secured. The mortality from some of 

 the most dreaded diseases has been reduced to an as- 

 tonishing degree, and, with the aid of sanitation, some 

 of them have become almost unknown. The achieve- 

 ments of medical bacteriology, too vast to be reviewed 

 here in detail, are only a promise of the still greater 



Fig. 2. Cylinders used for chemical and bacteriological investigations of soils. 



achievements to come, and a vindication of the views 

 set forth by the pioneers in the study, — Kohn, Pasteur, 

 Lister and Koch. 



Bactcrinlogij and agriculture. — In agriculture, the de- 

 velopment of bacteriology has given us a new insight into 

 the nature of soil fertilit)^ We have learned to regard 

 the soil as a culture medium with its almost endless 

 number of species and varieties of bacteria, specialized 

 to do important work in the transformation of soil, 

 nitrogen, carbon, hydrogen, sulfur; in the tran,s- 



