BACILLUS MESENTERICUS FUSCUS. 399 



opaque, while the lower part is clearer, and is only 

 rendered somewhat turbid by the presence of a few 

 flakes. On potatoes the bacilli form yellowish layers 

 with a flat surface and a dull paraffin-like appearance ; 

 later on the surface at the margin becomes drier, faintly 

 granular, and assumes a striped appearance as the result 

 of unevenness of the surface. The bacillus requires the Necessity cr 

 presence of oxygen to a greater degree than any of the oxygen - 

 other organisms as yet examined ; it only grows on the 

 surface, and ceases to form visible colonies, even when 

 there is a relatively trivial interference with the supply 

 of oxygen. 



Among the so-called potato bacilli, which readily grow 

 on the surface of potatoes, and which are often observed 

 as accidental contaminations, we have 



Bacillus mesentericus fuscus.* 



This organism occurs in the dust of hay, in the air, Brown potato 

 on the surface of potatoes, &c. ; it is very widely distri- bacillus 

 buted. The bacilli are small and short, often occurring in 

 chains of two to four members, and actively mobile ; they 

 form irregularly arranged, small, refracting spores. On 

 gelatine plates roundish, whitish colonies appear with 

 sharp contour under a low power, and later with delicate 

 processes of a yellowish brown colour, and finely granular 

 surface ; liquefaction of the gelatine rapidly occurs. In 

 puncture cultivations a whitish opacity is formed at first 

 along the track of the needle, and at the same time 

 there is a funnel-shaped area of liquefaction at the point 

 of entrance of the needle, this area extending within 4 

 to 6 days till it reaches the wall of the glass ; in this 

 way an upper layer of fluid is formed, in which whitish, 

 grey flakes are floating. On potatoes smooth yellowish 

 deposits appear on the first day, the surface of which, 

 however, become very quickly wrinkled and brown ; this 



* Gottinger hyg. Institut. 



