400 BACILLI WHICH APPEAE ON POTATOES. 



membrane is relatively thin, and does not extend deeply 

 into the substance of the potato. The growth rapidly 

 spreads over the whole surface of the potato. 



Bacillus mesentericus vulgatus.* 



Potato This organism is very widely distributed in nature ; 



it is usually, though badly, described under the name 

 "potato bacillus." The. bacilli are thick and large, 

 often forming pseudo-threads and spherical spores ; they 

 have an oscillating movement. On gelatine plates the 

 colonies present a bluish-white appearance, they are 

 almost transparent, but later the centre acquires an 

 opaque white colour ; the superficial colonies can attain 

 the diameter of almost 1 cm. These colonies sink to 

 some extent into the liquefied gelatine ; under a low 

 power they pre'sent the appearance of dark, distinctly 

 granular discs, with rough borders. The gelatine is 

 energetically liquefied. In puncture cultivations a 

 funnel-shaped area of liquefaction is formed at first, but 

 later the whole of the upper part of the gelatine becomes 

 . fluid ; in the fluid there are numerous grey flakes, and 

 on it there is a delicate greyish-white wrinkled skin. 

 At the bottom of the area of liquefaction a thicker floccu- 

 lent mass is present; from that point downwards we 

 still see, for the next few days, the remains of the line 

 of puncture, clothed with a thick whitish deposit. On 

 potatoes a whitish thick growth is formed which is 

 almost from the first markedly wrinkled, and .which 

 spreads rapidly over the whole, surface ; if we attempt 

 to pick up a portion of this skin it is seen that the 

 colonies have grown deeply into the substance of the 

 potato ; the raised portions of the skin remain in con- 

 nection' with the substance of the potato by a tough 

 mucous mass, so that long threads may be drawn out. 

 According to Hueppe the bacilli are not able to form any 

 ropy substances from sugar, but they have an energetic 

 diastatic action ; they also cause coagulation of casein 



* Gottinger hyg. Institut. 



