280 VETERINARY BACTERIOLOGY 



Physiology. B. typhosus develops best at a temperature of 

 37, but will grow at room-temperature. It is an aerobe and 

 facultative anaerobe. No indol is produced. Acid, but no 

 gas, is formed from dextrose. Neither acid nor gas is produced 

 from lactose or saccharose. There may be slight initial acidity in 

 milk, but there is never coagulation of the casein. Proteolytic 

 enzymes are not developed in cultures. 



Pathogenesis. Experimental Evidence. The lesions typical of 

 typhoid in man are not produced either by injection or feeding 

 experiments upon the laboratory animals. The symptoms after 

 intraperitoneal injection of a guinea-pig do not differ greatly 

 from those produced by the Bacillus coli. Feeding experiments 



** , ~* p Jr . . u 



m^ :^--.''- v ^fl* " 



D 





V ^f 



% 



Fig. 116. Bacillus typhosus, showing Fig. 117. Bacillus typhosus, colony on 

 flagella (Gunther). agar (Gunther). 



with anthropoid apes within recent years have shown the possi- 

 bility of producing the typical lesions of the disease in these 

 animals. Infection with typhoid bacilli in laboratory workers 

 has several times occurred following the accidental ingestion of 

 pure cultures of the organism. 



Character of Lesions and Disease Produced. Clinical diagnosis 

 of typhoid is frequently difficult, as the characteristics of the dis- 

 ease are often not well marked. The organism invades the in- 

 testinal lymph-system, and particularly the Peyer's patches. 

 The latter become ulcerated, and perforation of the intestinal wall 

 is a not uncommon result. The spleen is swollen. The bacteria 



