114 THE ACUTE SELF-LIMITED INFECTIONS 



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 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 



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



(Park.) 



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 bacillus. The 

 bacillus belongs to the so-called typhocolon group (see 

 p. 157). The lower animals do not develop typhoid fever 

 when inoculated with this germ, but die of septicemia, usually 

 with peritonitis. 



Immunization. An antitoxin to the typhoid bacillus 

 cannot be produced, but attempts at active immunization 



