BACILLUS TYPHOSUS. 



157 



rounded extremities, from 2 to 4 mikrons in length, and 0.6 to 

 0.8 mikron in breadth. At times it appears as short ovals ; at 

 others the bacilli are joined together, forming long threads. 

 It stains with all the anilin dyes, but not quite so readily as 

 other bacteria. It does not stain by Gram's method. In 

 stained preparations clear spaces are observed in the body of 

 the cells. This has given rise to the belief that the bacteria 

 contain spores. There are, however, no spores, for those clear 

 spaces do not stain by any of the spore-staining processes, and 

 bacteria in which they are found are less resistant to external 



FIG. 63. 



FIG. 64. 



/', 



Wtof 



Bacillus typhosus, from culture 

 twenty-four hours old, on agar- 

 agar. (Abbott.) 



Bacillus typhosus, showing flagella 

 stained by Loeffler's method. (Abbott.) 



influences than others. This bacillus has numerous fine, hair- 

 like flagella, which are not to be seen in unstained prepara- 

 tions or preparations stained by the ordinary methods, but 

 it requires the flagella-stain of Loeffler to bring them out. 



Biologic Characters. The Bacillus typhosus is aerobic, but 

 grows also without the presence of oxygen ; it is therefore 

 facultative anaerobic. It is non-spore-bearing, and is actively 

 motile, the motions at times being very rapid. It grows in 

 nearly all the artificial media, even at the room temperature, 

 but best at a temperature of 37 C. Its growth at 20 C. is 

 rather slow, but quite rapid at the temperature of the body. 



On gelatin plates its colonies appear as small, yellowish, 

 punctiform bodies, becoming in a short time round and 



