8 Bacteria in Relation to Country Life 



he found that the organisms could be grown on solid 

 substances, among them boiled potatoes. The bacterial 

 masses which appeared on the potatoes could be em- 

 ployed for infection of new portions of sterile potato, 

 whereby the distinct colors could be maintained. For 

 this reason, Schroter was inclined to think that he was 

 dealing with definite kinds of bacteria. 



The nucleus was thus created for the opinion that, 

 ' among bacteria, as among more highly organized or- 

 ganisms, there exist definite species fairly constant in 

 their structure and in their physiological activities. 

 This opinion was given expression by Ferdinand Kohn, 

 whose investigations and writings may be justly marked 

 as the beginning of a new period in modern bacteriology. 

 We owe to him not only the foundation of systematic 

 bacteriology, but the stimulus and the methods for 

 more advanced research. On this foundation, the genius 

 of his pupil, Robert Koch, built a noble structure and 

 established the science of bacteriology. 



Anthrax bacillus. — In 1876, Koch demonstrated 

 clearly and convincingly that anthrax in cattle is due 

 to a specific germ, and thus confirmed a fact already 

 indicated by the observations of others. He isolated 

 the anthrax bacillus in pure culture, studied it under 

 the microscope, and showed that he could produce an- 

 thrax in other animals by inoculation from such cultures. 



New methods of study. — Soon after this, Koch devel- 

 oped new methods for the study of bacteria, and for 

 the preparation of pure cultures. By the employment 

 of sohd media, he demonstrated the comparative ease 

 with which a number of di£ferent bacteria in the same 



