130 



generic names Fenohacter and Saccharohader) and to the groups of the 

 butyric acid and of the lactic acid bacteria. 



Within the genus Aerobacter Beijerinck recognized four different 

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

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

 forming abihty 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. infusionum, for a form frequent in plant infusions and in water 

 polluted with vegetable remains. 



The fourth species, Aerobacter liquefaciens, is worthy 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 f act 

 that the cells of this species are motile with 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 Kühr 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 Kühr 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 Voges and Proskauer reaction^). 



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 



1) For the description of these species one shoiild also compare Beijerinck's 

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



2) C. A. H. VON WoLZOGEN KüHR, Zcntralbl. f. Bakt. Tl, 85, 223, 1932. Recently 

 Kluyver and van Niel have gone so far as to create a new genus: Aeronionas for the 

 PseM6?owowas species having the type of fermentation characteristic of Ps. fermentans. 

 Cf. A. J. Kluyver and C. B. van Niel, Zentralbl.,f. Bakt. II, 94, 369, 1936. 



3) Cf., however, A. J. Kluyver and E. L. Molt, Proc. Kon. Ned. Akad. v. Wet. 

 Amsterdam 42, 118, 1939. 



