THE COLON-TYPHOID GROUP 139 



they are more persistent. Sewer-gas or air is never a source 

 of infection. 



Mode of Infection. The bacilli in the dejecta of the dis- 

 eased person find their way into drinking-water, milk, or 

 dirty clothes, and so into the alimentary tract of a person 

 predisposed to the disease. Flies act as conveyors by infect- 

 ing food. The bacilli enter the blood through the lymphatics, 

 and so become lodged in various organs^ They are quite 

 resistant, living for some time in the soil and water, and are 

 more resistant than other organisms to the action of phenol. 

 An epidemic has been traced to the eating of oysters taken 

 from contaminated water. Milk-cans washed in polluted 

 water may be the origin of an epidemic. Ice is rarely a cause. 



Pathogenesis. Lower animals do not have enteric fever, 

 though their death has been caused by injection of the bacilli 

 into the veins of the ear and peritoneum due to toxic substance. 



In man the bacillus has been found in the urine, blood, spu- 

 tum, milk, intestinal discharges, roseolar spots, and in various 

 organs, as spleen, liver, lymphatic glands, and intestinal villi. 



It is found in secretions several days after the attack has 

 subsided. It is found in this disease only. 



Typhoid Carriers. Some individuals retain a culture of 

 the bacilli in the gall-bladder for years, and manufacture, or 

 at least expel, true virulent bacilli through the feces and urine 

 intermittently. Such persons have infected other individuals 

 without suffering any inconvenience themselves. Some 

 forms of chronic inflammation, as cholecystitis and appen- 

 dicitis, have been caused by the typhoid bacillus, though 

 more often the colon bacillus is found. 



Products. Brieger found a substance in the cultures, 

 which he named typhotoxin, with the formula CgHnNCfe. 

 It has no specific action. A toxalbumin insoluble in water has 

 also been isolated, but, as experiment animals are immune to 

 the disease, no definite actions have yet been determined. 



The cultures, when old, show an acid reaction. 



Antityphoid bacterins (vaccines) have been used very ex- 

 tensively in armies and institutions as a prophylactic or pro- 



