28 DEVELOPMENT OF BACTERIOLOGY 



many yet unanswered. Still they are vital questions, for, in many 

 cases, the crop yields will be determined by the skill with which 

 these various changes are controlled. There is another set of organ- 

 isms in the soil, the function of which is to take the practically 

 valueless nitrogen of the atmosphere and change it into forms such 

 as the higher plants can feed upon. How may we control them for 

 maximum yields? For if treated properly they will never tire, but 

 toil on forever. Then again it is possible that bacterial action may 

 be used as a measure of soil fertility and methods so perfected which 

 are more sensitive than any now in use. Truly, in this field great 

 things have been accomplished, but there remains yet to conquer 

 fields richer by far than the workers of the past have ever dreamed. 



REFERENCES. 



Locy: Biology and its Makers. 



Paget: Pasteur and after Pasteur. 



Gregory: Discovery The Spirit and Service of Science. 



Vollery-Radot: The Life of Pasteur. 



Libby: History of Science. 



