48 Prof. R. Boyce and Mr. A. E. Evans. [Feb. 23, 



II. " Upon the Action of Gravity on Bacterium Zopfii" By 

 Rubert Boyce, M.B., Assistant Professor of Pathology, 

 University College, London, and A. Ernest Evans, M.B., 

 CM., Glasgow. Communicated by Professor Horsley, 

 F.R.S. Received February 7, 1893. 



(From the Pathological Laboratory of University College, London.) 



(Abstract.) 



Bacterium Zopfii was accidentally discovered by Kurth, in Zopf s 

 laboratory, in the alimentary canal of the fowl. He showed it to be 

 pleomorphic, and observed its radiate mode of growth, and, in addi- 

 tion, its great tendency to form spirals. It was rediscovered by 

 Crookshank in Johne's laboratory in Dresden ; this observer obtained 

 it from the air, and likewise noted the characteristic pinnate mode of 

 growth. He named it Bacterium figurans, on account of its figured 

 appearance upon the solid nutrient media. We obtained it from a 

 case of otitis media in the cat, in London. These observations show 

 that the organism is probably widespread. 



Mode of Growth of the Bacterium. — On gelatine it forms, under 

 certain circumstances, a feather-like or pinnate growth upon the 

 surface and in the gelatine, the branches of which are directed 

 upwards at about an angle of 45°. Under no circumstances (accord- 

 ing to our observations) does it form a pinnate growth upon agar or 

 potato. 



Action of Gravity. — The symmetrical pinnate growth could not be 

 obtained in gelatine tubes which were kept horizontal or nearly so, 

 whilst similar tubes kept vertical or nearly so exhibited the character- 

 istic growth. A certain scale of symmetry could be obtained by 

 placing the tubes at various angles between the vertical and hori- 

 zontal. If a tube in which a pinnate growth had been obtained was 

 completely reversed, a new pinnate growth might be seen to cross 

 the first, but it was not so marked as the latter. These observations 

 showed that Bacterium Zopfii was markedly susceptible to position, 

 and that the pinnate growth could only be obtained in or about the 

 vertical. They pointed strongly to the influence of the action of 

 gravity. 



Behaviour on the Clinostat. — If the force of gravity acting upon the- 

 culture tube in the one position were prevented by slowly revolving 

 the growth in the vertical at rates from one revolution in one minute 

 to one in one hour, then the pinnate growth could not be obtained. 

 We assumed, therefore, that Bacterium Zopfii was subject to the 

 action of gravity, and that it was negatively geotropic. But if it were 



