462 MICHO-OEGATsISAL^ IN WATER 



BACILLUS MESENTERICUS RUBER 



I LI QUEFIES GELATINE | 



Authority. — Globig, ' Ueber einen Kartoffel-bacillus mit ungewohnlich 

 \viclerstamlsfahigen Sporen,' Zeitschrift f. Hygiene, vol. iii. p. 322. 



Where Found. — On potatoes, but also in water by various investigators. 



Microscopic Appearance. — Slender bacillus with rounded ends, occurring 

 in pairs, sometunes in fours, and so forming short threads. It is very motile. 

 Forms lustrous egg-shaped spores. This potato bacillus is slenderer than the 

 other potato varieties. 



Cultures.— 



Gelatine Plates.— After two days the depth colonies are seen, under a low 

 power, to be circular, smooth, and yellow or brown, sometimes dark brown 

 in colour. The surface colonies exhibit short fine threads, at first only at one 

 spot of the periphery, but later the remainder of the periphery is composed of 

 irregular threads, which bend and cross one another in all directions, whilst a 

 broad light expansion consisting of delicate network, the outermost edge of 

 which is provided with fine points, surrounds the original colony ; on the fourth 

 day liquefaction of the gelatine commences, the colony increases in size, the 

 network disappears, and the outline of the original colony becomes indistinct, 

 whilst light greyish brown masses are visible where the colony has expanded, 

 which assume a sort of star-shaped arrangement. To the naked eye at this stage 

 the colony looks bluish white, and forms liquid circular depressions. As soon 

 as the liquefaction begins spore formation commences. 



Gelatine Tubes. — Forms a flat funnel-shaped liquid depression, which soon 

 reaches the walls of the tube and extends slowly in the depth. The fluid 

 gelatine is slightly turbid, often contains fiocculent particles, whilst a thin 

 pellicle forms on the surface. 



Potatoes. — Grows differently according to the incubating temperature. At 

 about 15° C, on the third day, the whole surface is covered with a thin but 

 tough and stringy, yellow, flnely furrowed expansio;i. Spores are found on the 

 second day. At 37° C. the surface is covered in twenty-four hours by a reddish 

 or pink red growth, having an odour of boiled ham. In forty-eight hours the 

 growth has spread over the sides of the potato. It grows best at 45° C, but will 

 not develop at 50° C. 



Broth. — Grows only on the surface, forming a thick tough skin, whilst 

 beneath the liquid remains quite clear. 



BemarkB, — Mice and guinea-pigs were not affected by it. The spores resist three- 

 quarters of an hour's exposure in the steam steriliser, reaching a temperature of from 

 109^ to 113° C. They are killed by three minutes' exposure to 126'^ C. and two 

 minutes to 127° C.^ and at 130° C. are instantly kiUed. 



