322 



TYPHOID FEVER 



is no evidence that spore -formation occurs in the typhoid 

 bacillus. 



Mobility. In hanging-drop preparations the bacilli are found 

 to be actively motile. The smaller forms have a darting or 

 rolling motion, passing quickly across the field, whilst some show 

 rapid rotatory motion. The filamentous forms have an un- 

 dulating or serpentine motion, and move more slowly. Hanging- 

 drop preparations ought to be made from agar or broth cultures 



Fm. 1.12. Typhoid bacilli, from a young culture on agar, showing flagella. 

 Stained by Van Ermengem's method. x 1000. 



not more than twenty-four hours old. In older cultures the 

 movements are less active. 



Flagella. On being stained by the appropriate methods (vide 

 p. 103) the bacilli are seen to possess many long wavy flagella 

 which are attached all along the sides and to the ends (Fig. 112). 

 They are more numerous, longer, and more wavy than those of 

 the b. coli. 



Characters of Cultures. Stab cultures in peptone gelatin give 

 a somewhat characteristic appearance. On the surface of the 

 medium growth spreads outwards from the puncture as a thin 



