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by PRAZMOWSKI in 1880, which BEIJERINCK, in 1893, had also in- 

 corporated into his genus Granulobacter. Bacillus polymyxa has in 

 common with the other Granulobacter species that it is a spore-forming 

 rod which brings about a vigorous sugar fermentation. However, 

 Bacillus polymyxa occupies a very special position, because, unlike the 

 obligatory anaerobic butyric acid and the butyl alcohol bacteria, it 

 attains a good development under aerobic conditions and, therefore, 

 forms a transition to the aerobic, non-fermenting, spore-forming 

 bacteria of the genus Bacillus l ). 



The paper affords several points of interest. In the first place it 

 throws much light on the wide occurrence of Bacillus polymyxa in na- 

 ture, and it describes also suitable enrichment procedures facilitating 

 its isolation. The main point of interest, however, is the study of the 

 conditions which determine the production of large amounts of mucus 

 by the bacterium, a property which, having already been observed by 

 PRAZMOWSKI, was responsible for the specific name of the organism. 

 BEIJERINCK and DEN DOOREN DE JONG proved that this production 

 of a slime of carbohydrate nature is due to a lack of balance in the 

 nutritional factors : a shortage of assimilable nitrogenous substances in 

 presence of an excess of carbohydrate in the medium being especially 

 favourable for the formation of the mucus. The demonstration that 

 the mucus, once formed, is consumed again by the bacterium itself on 

 addition of a nitrogenous compound, like asparagine, and is then 

 converted into new cell material, is particularly convincing in this 

 respect. There is no doubt that the same situation obtains with many 

 slime-producing bacteria. Several recent studies on bacteria of this 

 type might have been influenced for the better, if the investigators 

 performing them had been acquainted with the fundamentally im- 

 portant observations referred to above. 



i. The genus Aerobacter Beijerinck. 



After what has been reported on BEIJERINCK'S work on the lactic 

 acid and the butyric acid bacteria, it seems only natural for BEIJE- 

 RINCK to have given due attention to the third important natural 

 group of sugar-fermenting bacteria, frequently known by its vulgar 

 name of "colon group". Yet, BEIJERINCK'S communications regarding 

 his experiences with the representatives of this group are chiefly 

 confined to one publication which first appeared in 1900 2 ). The title 

 of the paper, "Sur la formation de I'hydrogene sulfure dans les ca- 

 naux, et le genre nouveau Aerobacter", would make one conclude that 



') The situation outlined above has made DONKER decide to unite Bacillus poly- 

 myxa together with a few other related species into a new genus for which the name 

 Aerobacillus was proposed. Cf. H. J. L. DONKER, Bijdrage tot de kennis der boter- 

 zuur-, butylalcohol- en acetongistingen. Delft, 1926. 



2) Centralbl. f. Bakt. u. Parasitenk. 11,6, 193, 1900. A somewhat extended version 

 was published in: Arch, neerl. d. sciences exactes et naturelles Ser. II, 4, 7, 1901. 



