BACILLUS TYPHOSUS 125 



Morphology. The typhoid bacillus is a motile rod 

 Y5 W IT to -g oV <y inch long and TTO Iro <r to iro"r<nr incn wid e, 

 with rounded ends, growing in long threads at times. 

 Its motility is due to flagella all around its cell wall. 

 It forms no spores. It stains easily, oftentimes more 

 densely at the rounded ends. It grows in the presence 

 or absence of oxygen, best at 37 C. or 98 F., but also 

 at room temperature. It is killed by heating at 60 C. 

 or 142 F. for five minutes, or to 52 C. or 126 F. for 



FIG. 37. Typhoid bacillus with faintly stained flagella. (Loffler's 

 method.) (Park.) 



ten minutes when in water suspension. It usually dies 

 rapidly when dried, but occasionally lives for some 

 weeks. It is killed in watery suspension by 1 per cent, 

 carbolic acid or 1 to 1000 bichloride in ten minutes. Its 

 characters in laboratory culture media are not easy to 

 describe, and indeed the trained observer is often 

 puzzled to identify it. Suspected cultures are usually 

 subjected to the Widal test, using the blood of a patient 

 with typhoid fever, and known to clump a true typhoid 



