Bacillus Typhi-exanthematicus 581 



Staining. — It stains ordinarily and is Gram-positive. It is not acid-fast. 



Ctdlivalion. — The organism is an obligatory anaerobe. It grows only at 37°C., 

 better on solid than in fluid media, the best growth resulting from the use 

 of o.s per cent, glucose serum-agar. Upon plates under anaerobic conditions 

 in a Novy jar, colonies developed after seven days. They attained a size of 1.5- 

 2 mm., were round or oval, were cream-colored by reflected light, opaque by trans- 

 mitted light. 



The bacillus produces acid from glucose, maltose, galactose and inulin; no 

 acid from raffinose, mannite, arabinose, saccharose, dextrin or lactose. No vis- 

 ible gas results from the transformation of any of these carbohydrates. 



No growth occurs in gelatin; an "invisible growth" occurs on potato. 



Thermal Death Point. — This was found to be SS°°C. maintained for ten minutes. 



Pathogenesis.— "^htn inoculated into guinea pigs the same symptoms were 

 observed as followed inoculation with typhus blood — i.e., fever terminating by 

 crisis. 



Complement-fixation. — Complement-fixation tests were positive in six out of 

 eight cases tried, but only after the crisis of the disease had taken place. 

 There was no complement-fixation with any of thirty-six bloods used as controls. 



