The Action of Gravity upon Bacterium Zopfii. 301 



regular growth of delicate white filaments. Re-inoculation proved 

 the presence of more than one micro-organism, but we soon succeeded 

 in isolating one which did not liquefy the gelatine, and which pre- 

 sented the exceedingly characteristic feather-like appearance well 

 known to belong to Bacterium Zopfii. We were especially struck by 

 the beautiful regular upward growth of the filaments upon the 

 gelatine surface, for whether we placed the tubes with their mouth 

 pointing upwa.rds or downwards there appeared the same definite 

 growth, provided the tubes were kept in a nearly vertical position. 

 We accordingly immediately commenced an investigation, which we 

 hoped might throw some light upon the meaning of this very definite 

 symmetrical growth. With this end in view we first investigated the 

 action of light, but whether we grew the bacterium in the light or in 

 the dark, the symmetry remained the same. We now began to ob- 

 serve, however, that tubes which, after inoculation, were kept in a 

 horizontal position exhibited an irregular growth. It therefore 

 occurred to us to test the action of gravity, and we found in effect that 

 revolving inoculated test-tubes slowly upon the clinostat* produced 

 irregular growths, whilst centrifugal force induced, like gravity, a 

 regular growth. Bacterium Zopfii was therefore negatively geotropic. 

 These phenomena, viewed in the light of the more recent experi- 

 ments upon the chemotactic and physiotactic properties of protoplasm 

 properties which appear already to throw very considerable light upon 

 certain pathological problems have led us to venture to record in 

 detail our observations. 



Bacterium Zopfii was accidentally discovered by Kurthf in the 

 alimentary tract of the hen in 1883, and his description of the micro- 

 organism, furnished from Zopf's laboratory, remains the standard 

 one. In 1885 Professor CrookshankJ obtained from the air in Johne's 

 laboratory an organism which he named Bacillus figurans on account 

 of its characteristically figured growth upon gelatine and agar; it 

 proved to be identical with Kurth's bacillus. Lastly, as previously 

 mentioned, we obtained our growth from the middle ear of the cat. 

 These observations make it very probable that Bacterium Zopfii has a 

 wide distribution, but whether it is pathogenic or not is still uncertain. 

 We will, however, return to this point later on. 



Bacterium Zopfii is pleomorphic ; it is a slender organism of about 

 the same diameter as Bacillus anthracis, and its segments are of very 

 variable length. It occurs in the dissociated motile state, the 

 elements being actively movable coccal, bacteroid, bacillary, and 



* We desire to express our thanks to Professor Oliver for not only the use of this 

 and other instruments, but also for his friendly criticism and advice during the 

 research. 



f ' Bot. Zeitung,' 1883. 



$ ' Lancet,' 1885. 



T 2 



