THE COLON-TYPHOID SBEIES 341 



nor gas from lactose or sucrose. Milk is not coagulated and 

 proteolytic enzymes are not produced. 



The cultural and physiologic reactions make it possible 

 to isolate the typhoid bacillus directly from the stools of 

 infected individuals and, by a process somewhat more 

 arduous, from infected water or sewage. Many special dif- 

 ferential media have been developed to permit the ready 

 isolation and identification of the organism. "When pure 

 cultures have been secured, the final test usually employed 

 is agglutination by means of a specific anti-typhoid serum. 



Disease Produced. — Typhoid fever is a disease charac- 

 teristic of man and is not produced readily by either injec- 

 tion or by feeding of cultures to laboratory animals. The 

 organism apparently develops first in the contents of the 

 intestine, then invades the intestinal wall and the Peyer's 

 patches. These latter frequently become ulcerated and 

 occasionally perforation of the intestinal wall may result. 

 The organisms are present in considerable numbers in the 

 blood stream ; in fact, the disease is frequently characterized 

 as a bacteremia. The spleen is considerably swollen. Infec- 

 tion of the gall bladder is not infrequent. 



The typhoid bacteria leave the body almost exclusively 

 with the stools and occasionally with the urine. The bac- 

 teria do not multiply to any extent (if at all) in nature out- 

 side of the body; in fact, they die out with considerable 

 rapidity after leaving the alimentary tract. Infection of 

 another can occur only by swallowing typhoid germs. It is 

 evident, therefore, that the prevention of typhoid fever 

 depends upon preventing the ingestion of typhoid bacilli 

 which have been voided comparatively recently by those 

 having the disease or by so-called bacillus carriers. A 

 bacillus carrier is a person who harbors pathogenic organ- 

 isms such as typhoid bacilli without showing symptoms of 

 disease. Usually those who have typhoid fever eliminate 

 the organisms completely and do not show them in their 



