BACILLUS AEROGENES CAPSULATUS 473 



sesses a capsule which, however, can not be constantly demonstrated. 

 The capsules are best seen when preparations are made from animal 

 fluids, but can often be demonstrated in those stained from artificial 

 cultures. They are demonstrated best by one or the other of the 

 ordinary capsule stains. 



The bacillus is stained easily by the usual anilin dyes. In tissue 

 preparations, the bacilli regularly retain the gentian-violet when stained 

 by Gram's method. In smears from artificial culture media, while 

 most of the bacilli stain by Gram, many will be seen wholly or partially 

 decolorized, owing probably to the rapid production of involution forms. 



Cultivation. — Bacillus aerogenes capsulatus is an obligatory anaerobe. 

 The first cultivations by Welch and Nuttall were made in deep agar 

 stabs. It grows well upon all the usual media, preferring a neutral or 

 sUghtly alkaUne reaction. All media are improved for the cultivation 

 of this bacillus by the addition of glucose, lactose, or some other easily 

 fermented carbohydrate. 



Upon agar or gelatin plates, growth appears at 37.5° C. within 

 twenty-four hours, as a flat, grayish translucent round disk. The 

 margins of colonies are slightly irregular and fringed. Gelatin is slowly 

 liquefied by the large majority of cultures, but Welch states that occa- 

 sionally liquefaction does not occur. 



In deep agar stabs or in agar slant cultures, especially in those con- 

 taining a carbohydrate, there is a rapid formation of gas bubbles, a 

 characteristic which is especially well developed and lends the cultures 

 of this bacillus their chief diagnostic feature. 



In hroih, growth is heavy and abundant. At first there is general 

 clouding. Within forty-eight hours, however, a heavy, white, flocculent 

 sediment is formed. Owing to the formation of gas, broth tubes if 

 undisturbed usually show a light froth of bubbles on the surface. 



On potato, growth is scanty and the medium possesses no advantages 

 either for cultivation or diagnosis. On coagulated blood serum, growth 

 is heavy and rapid and this medium is especially adapted for spore 

 formation. There is slight peptonization of the blood serum. In milk, 

 there is rapid coagulation, rapid acidification, and gas formation. 



The carbohydrates, glucose, lactose, and saccharose, are fermented 

 by this bacillus. Mannit is apparently not fermented. 



Welch and Nuttall state that the bacillus is capable of producing gas 

 from proteid matter. The gas formed, according to Dunham,' consists of 



' Dunham, loc. cit. 



