PATHOGENIC BACTERIA 137 



rarely fatal. They may be the sole cause of the disease, 

 and also occur together with the typhoid bacillus in mixed 

 and secondary infections. Morphologically, they resemble the 

 typhoid bacillus, but differ from it culturally and give their 

 own serum reactions with the blood of affected patients. They 

 ferment glucose, but not lactose or saccharose; litmus milk at 

 first becomes acid, but later grows alkaline and is not coagu- 

 lated. On potato a slight visible growth occurs; indol is usually 

 not formed. Typhoid serums do not agglutinate paracolon 

 bacilli, and vice versa; also different paracolon infections may 

 not agglutinate each other. The Bacillus enteritidis of 

 Gartner is a related form. 



Bacillus psittacosis is an allied form occurring in parrots, 

 and producing hemorrhagic septicemia in them and other experi- 

 ment animals. The disease is readily communicated to man 

 from the affected birds, and causes, after ten days' incubation, 

 a disease, the chief symptoms of which are fever, delirium, 

 vomiting, diarrhea, and albuminuria, about a third of the 

 cases ending fatally. The organism is agglutinated by strong 

 dilutions of typhoid serum, but the clumping is incomplete and 

 the bacillus differs further from the typhoid bacillus in its 

 growth on potato and in the nature of the infection produced. 



Bacillus Coli Communis (Escherich). Found in human 

 feces, intestinal canal of most animals, in pus and water. 



Form. Short rods with very slow movement, often asso- 

 ciated in little masses resembling the typhoid germ, flagellated, 

 not forming spores (Fig. 70) . 



Properties. Does not liquefy gelatin, causes fermentation in 

 saccharine solutions in the absence of oxygen, produces acid 

 fermentation in milk, causes formation of indol in peptone 

 solutions; its optimum temperature for growth is 37 C. 



Growth. On potato a thick, moist, yellow-colored growth; 

 on agar a gray-white growth; on gelatin a growth similar to 

 typhoid. It can also develop on phenol-gelatin, and withstands 

 a temperature of 45 C. without its growth being destroyed. 



Patho gene sis. Inoculated into rabbits or guinea-pigs, death 

 follows in from one to three days, the symptoms being those of 



