CHAPTER XXI 



A MORE DETAILED APPRECIATION OF BEIJERINCK'S 

 MAIN CONTRIBUTIONS TO MICROBIOLOGY 



Although in the previous chapter a general outline already has 

 been given of the eminent services rendered by BEIJERINCK to the 

 science of microbiology, the picture of this great scientist would re- 

 main incomplete if no attempt was made to describe with more detail 

 a number of the more important discoveries made by BEIJERINCK in 

 the microbiological field. Herefor the major problems dealt with by 

 BEIJERINCK will successively be passed in review, and since BEIJE- 

 RINCK'S occupations with one and the same problem are often widely 

 separated in time, the survey as a whole will no longer adhere to 

 chronology. 



a. The isolation and investigation of Bacillus radicicola. 



In one of the laboratory note-books (Div. "Bacteria" No. 4), left 

 behind by BEIJERINCK, one finds under the date of May 25th, 1887, a 

 simple entry which on translation reads: "Bacteroids of Vicia Faba; 

 those of Pisum sativum almost identical. For Trifoliwn pratense small 

 round vesicles." Simple drawings illustrate these statements. The 

 following entry is that of May 3 1 st in which it is reported that on May 

 26th a small quantity of a ground-up nodule of Vicia Faba was sown 

 on a solid culture medium made by adding gelatine to a decoction of 

 the roots of the same plant. 



The particular page of the laboratory note-book has been reproduc- 

 ed in Plate XII. 



This was the beginning of an enormous amount of experimental 

 work leading to the isolation of Bacillus radicicola and to the ex- 

 perimental proof that this bacterium - or closely related varieties 

 and species - - is responsible for the formation of the nodules on the 

 roots of Leguminosae in general. 



Which factors are responsible for this sudden interest of BEIJE- 

 RINCK for the problem in question? On the one hand it is easily 

 understood that the mystery of the root nodules was already puzzling 

 BEIJERINCK'S mind since a long time. We have only to realize that 

 in a former period he was above all a cecidologist, and that the inter- 

 pretation of the root nodules as a special type of plant gall was at 

 that time unreservedly accepted. In BEIJERINCK'S doctorate thesis, 

 which appeared in 1877, the following passage occurs: "Slechts in 



