141 



experiments made according to exactly the same principle led to so 

 different results in the hands of the two investigators. 



Beijerinck mentions in the first place as a point of difference that 

 he took measures to promote the aerobic conditions in the medium. 

 However, these measures appear to have been confined to the use of 

 thin layers of culture medium in large Erlenmeyer-f lasks, and this was 

 exactly Winogradsky's procedure. It is, moreover, stated explicitly 

 that the mode of renewing the air in the culture flask was the same as 

 in Winogradsky's experiments. So here no explanation of the differ- 

 ence in results can be found. 



The second difference in procedure stressed by Beijerinxk is the 

 use of other carbon sources. Beijerinck remarks in this connection 

 that in order to suppress butyric acid fermentation in the medium he 

 has replaced the glucose by substrates, like mannitol and various 

 propionates, the first-named compound being only with difficulty 

 fermentable by butyric acid bacteria, and the propionates not at all. 



There seems no doubt that indeed Beijerinck's natural tendency 

 to vary widely the composition of the media used by him is directly 

 responsible for his discovery of the new group of nitrogen fixing 

 organisms, which he well may have first observed in media containing 

 one of the substrates mentioned above. However, this explanation is 

 quite inadequate to make comprehensible why Winogradsky should 

 not have observed the same organisms six years earlier. For although 

 Beijerinck rightly maintains that media containing mannitol or 

 propionate have the advantage that in these media the anaerobic 

 spore-forming organisms develop more slowly than in glucose media, 

 yet, every student of soil microbjology will be prepared to confirm 

 that as a rule Azotobacter develops in an equally abundant way in 

 enrichment cultures made with media containing glucose and calcium 

 carbonate. 



This point of view is fuUy confirmed by Winogradsky himself. 

 Beijerinck's communication seems to have revived his interest in 

 theprobleminquestion, for the next year he pubhshed in the "Cen- 

 tralblattfür Bakteriologie" another extensive memoir on Clostridium 

 Pastorianum i). 



As motive for this sudden activity after seven years of silence 

 Winogradsky mentions that he often received inquiries from col- 

 leagues regarding the identity of certain strains with Clostridium 

 Pastorianum and thus concluded that the description of the said 

 species in his 1895 paper was not sufficiently complete. He then gives 

 a very detailed survey of the morphological and fermentation proper- 

 ties of the organism. In connection with the question under discussion 

 the supplement is by far the most interesting part of the publication. 

 Herein he gives his reflections on Beijerinck's recent pubhcation. In 



1) S. Winogradsky, Centralbl. f. Bakt. u. Parasiten4c. II, 9, 43 und 107, 1902. 



