9 6 



PHARMACEUTICAL BACTERIOLOGY. 



a few others. Of these, Rhizobium mutabile, the root-nodule bacterium of 

 the Leguminosae, has received most attention. 



The first to suggest a plan for practically utilizing the root nodule bacteria 

 (Rhizobia) and to secure letters patent for the process in Germany and the 

 United States, were Nobbe and Hiltner, of Tharand, Germany. Patent 

 No. 570,876 was granted Nobbe and Hiltner in the United States, November 

 3, 1896. This patented fertilizer for leguminous plants consisted of pure 

 cultures of the several varieties (or perhaps species) of R. mutabile, each spe- 

 cies of plant, as bean, pea, clover, alfalfa, etc., having the cultures derived 

 from the root nodules peculiar to it. 



FIG. 45. Root nodules of sweet clover, somewhat magnified. A, rootlets with 

 nodules, a, single nodules, b, clusters of nodules. These are sometimes very large, 

 consisting of hundreds of nodules, loosely united. B, diagram of single nodule, a, un- 

 infected area, b, infected area. 



This commercial preparation was given the name "nitragin," and its 

 efficiency was quite carefully and extensively tested and commented upon 

 by European and American investigators. The consensus of opinion seems 

 to be that it was of doubtful practical utility for agricultural purposes. 

 Some authorities maintained that it was of unquestionable value in virgin 

 soil. In rich and otherwise favorable soil conditions it is of only slight value. 

 It is maintained that nitragin aids very materially in developing and ripening 

 the fruit. As becomes evident from careful consideration, the value of 

 this microbic fertilizer depends upon whether or not it will cause an increased 

 development in the number and size of root tubercles over and above those 

 which would develop without the presence of this artificial aid. If the soil 



