130 



generic names Fenobacter and Saccharobacter) and to the groups of the 

 butyric acid and of the lactic acid bacteria. 



Within the genus Aerobacter BEIJERINCK recognized four different 

 species '). For the first two species, viz., A. aerogenes and A. viscosum, 

 which may be easily distinguished on the ground of the strong slime- 

 forming ability of the latter, a simple enrichment procedure is des- 

 cribed. The third species Aerobacter coli is the typical organism pre- 

 dominating in human faeces. In this species BEIJERINCK created the 

 var. infiisionuin , for a form frequent in plant infusions and in water 

 polluted with vegetable remains. 



The fourth species, Aerobacter liquefaciens , is \vorthy of some 

 special attention. It differs from the foregoing species by its ability 

 to bring about marked liquefaction of gelatine. Another characteristic 

 of this species did not escape BEIJERINCK'S attention, viz., the fact 

 that the cells of this species are motile \vith the aid of one polar flag- 

 ellum, in contrast to what holds for the other species, strains of which, 

 if motile, have peritrichous flagella. 



At that time this difference was judged to be not incompatible 

 with generic identity. In later years, such a difference has usually been 

 deemed to be of decisive significance for the separation of natural 

 groups. It was mainly from the type of flagellation that VON WOLZO- 

 GEN RUHR decided to incorporate the fermenting organism with polar 

 flagella, isolated by him, into the genus Pseudomonas 2 ). There seems, 

 nowadays, little doubt that the bacterium described by KUHR as the 

 new species Pseudomonas fermentans is identical with BEIJERINCK'S 

 Aerobacter liquefaciens. 



On concluding this survey of the genus Aerobacter, as outlined by 

 BEIJERINCK, it seems necessary, in order to avoid misunderstanding, 

 to observe that the generic name Aerobacter Beijerinck is used in a 

 much more restricted sense in the well-known American classification 

 of BERGEY et al. 



In this classification the genus embraces only those species which 

 produce acetyl methyl carbinol in the sugar fermentation and, there- 

 fore, give a positive VOCES and PROSKAUER reaction 3 ). 



j . Investigations on Sarcina ventriculi. 



Whilst the fermentation processes mentioned in the preceding 

 paragraphs have been known from the very beginning of the develop- 

 ment of bacteriology as a science, it was also given to BEIJERINCK to 



') For the description of these species one should also compare BEIJERINCK'S 

 paper on indigo fermentation in Proc. Kon. Akad. v. Wet. Amsterdam 2, 495, 1900. 

 V II. VON Woi./ock.x KUHR, Zentralhl. f. Bakt. II, 85, 223, 1932. Recently 

 KLUYVER and VAX NIKL have gone so far as to create a new genus: Aeromonas for the 

 Pseudomo nas species ha\ in <; 1 lie type of fermentation characteristic of Ps. fermentans. 

 ( I. A. J. Ki.rvvr i: and C. K VAN NIEL, Zentralbl. f. Bakt. II, 94, 369, 1936. 



3) ('!., however, A. [. KLUYVER and 1C. L. MOLT, Proc. Kon. Ned. Akad. v. Wet 

 Amsterdam 42, 118, 1939. 



