464 



CHOLEEA 



the following appearance : There is at the surface the bubble- 

 shaped depression ; below this there is a funnel-shaped area of 

 liquefaction, the fluid being only slightly turbid, but showing 

 at its lower end thick masses of growth of a more or less spiral 

 shape in the thin line of liquefaction (Fig. 1 38). (This appear- 

 ance is, however, in some varieties not produced till much later, 

 t especially when the gelatin is very stiff, 



and, in other varieties which liquefy very 

 slowly, may not be met with at all.) At 

 a later stage liquefaction spreads and may 

 reach the side of the tube. When the 

 organism is sub-cultured over a long period 

 of time, it may lose to a large extent the 

 property of liquefying gelatin. 



In gelatin plates the colonies are some- 

 what characteristic. They appear as minute 

 whitish points, visible in twenty-four to 

 forty-eight hours, the surface of which, 

 under a low power of the microscope, is 

 irregularly granular or furrowed (Fig. 

 139, A). Liquefaction occurs, and the 

 colony sinks into the small cup formed, 

 the plate then showing small sharply- 

 marked • rings around the colonies. Under 

 the microscope the outer margin of the cup 

 is circular and sharply marked. Within 

 the cup the liquefied portion forms a ring 

 which has a more or less granular appear- 

 ance, whilst the mass of growth in the 

 centre is irregular and often broken up at 

 its margins (Fig. 139, B). 



On the surface of agar media a thin, 

 almost transparent, layer forms, which 

 presents no special characters. On solidified 

 blood serum the growth has at first the 

 same appearance, but afterwards liquefac- 

 tion of the medium occurs. On agar 

 plates the superficial colonies under a low power are circular 

 discs of brownish-yellow colour, and more transparent than 

 those of most other organisms. On potato at the ordinary 

 temperature, growth does not take place, but on incubation 

 at a temperature of from 30° to 37° C. a moist layer appears, 

 which assumes a dirty brown colour, somewhat like that of 

 the glanders bacillus ; the appearance, however, varies some- 



FlG. 138. — Puncture 

 culture of the cholera 

 spirillum in peptone 

 gelatin — six days' 

 growth. Natural size. 



