448 



PATHOGENIC MICROORGANISMS 



or gelatin cultures. The capsule is usually large, twice or three times 

 the size of the bacillus itself. When seen in chains or in groups, several 

 bacilli may appear to be inclosed in one capsule. Prolonged cultivation 

 on agar or gelatin may result 'in disappearance of the capsule. The bacil- 

 lus is easily stained with the ordinary dyes, but is decolorized when 

 stained by the Gram-method. Capsules may often be seen when the 

 more intense anilin dyes are employed. They are brought out with much 

 regularity by any of the usual capsule stains. 



Cultivation. B. mucosus capsulatus is easily cultivated. It grows 



* 



FIG. 94. BACILLUS MUCOSUS CAPSULATUS. 



readily on all the usual culture media, both on those having a meat- 

 infusion basis and on those made with meat extract. Growth takes 

 place at room temperature (18 to 20) and more rapidly at 37.5 C. A 

 temperature of 60 C. and over kills the bacilli in a short time. The ther- 

 mal death-point according to Sternberg is 56 C. Growth ceases below 

 10 to 12 C. Kept at room temperature and protected from drying, 

 the bacillus may remain alive, in cultures, for several months. 



The bacillus is not very fastidious as to reaction of media, growing 



