SPIRILLUM CONCENTRICUM. 377 



and F. Cohn, but were never previously cultivated. 

 Kutscher himself described part of the same with a flat 

 bend to the spiral as vibriones, in spite of the fact that 

 he had stained the terminal, thick bunches of flagella. 



The isolation was accomplished by means of agar plates, 

 after a preliminary culture had been prepared which fur- 

 nished a surface pellicle containing spirilla, according to the 

 method employed in cholera diagnosis. The colonies sus- 

 pected of being spirilla were torn with a fine platinum wire 

 under the microscope and then it was noticed whether 

 upon slight magnification motion could be observed in the 

 drop of fluid which collected in the rent. If this was the 

 case, it could be conjectured that spirilla (or vibrios) were 

 being dealt with, since the ordinary micro-organisms of 

 manure were almost all non-motile. 



Kutscher employed as nutrient medium, meat infusion agar, neu- 

 tralized with soda, without any further addition. Zettnow finds the 

 additions of 0.1% ammonium sulphate and 0.1% potassium nitrate 

 to be practical, and gives detailed descriptions for the preparation of 

 " spirilla-agar " (C. B. xix, 393). 



Spirillum concentricum. 1 Kitasato (C. B. iii, 72). 

 (Plate 55, vi-ix.) 



Short, more or less winding spirals, 1-8 P. long and 0. 5 fj. 

 thick, actively motile, 2 staining by Gram's method (55, 



IX). 



Upon gelatin plates delicate, transparent growths, finely 

 punctated (55, vn). In the gelatin and agar stab a 

 spindle-shaped growth below the surface, similar to the 

 Spirillum rubrum, but yellowish. Upon the agar plate, 

 delicate (according to Kitasato, firmly adherent) colonies, 

 opaque and yellowish in the center, and at the border trans- 

 parent and finely granular (55, vi). Bouillon is rendered 



1 The name was given by Kitasato on account of the very charac- 

 teristic cockaded growth in gelatin cultures ; our plates show nothing 

 of it. 



2 In spite of every precaution our cultures never showed the active 

 motility observed by Kitasato. We have never tried to stain flagella. 

 Loffler has described terminal bunches of flagella. 



