Pathogenesis 639 



poisonous fractions by extracting massive cultures of typhoid 

 bacilli with 2 per cent, solutions of sodium hydrate in abso- 

 lute alcohol at 78 C. 



Mode of Infection. The typhoid bacillus enters the body 

 by way of the alimentary tract with infected foods and drinks. 



Rosenau, Lumsden, and Kastle* were able to connect 10 

 per cent, of the cases occurring in the District of Columbia 

 with infection through milk. Interesting additional facts 

 upon the subject can be found in Bulletin No. 41 of the 

 Hygienic Laboratory upon "Milk in its Relation to the 

 Public Health." The bacillus occasionally enters milk in 

 water used to dilute it or to wash the cans. 



The occurrence of typhoid fever among the soldiers of the 

 United States Army during the Spanish-American War in 

 1898 was shown by Reed, Vaughan, and Shakespeare f to 

 be largely the result of the pollution of the food of the soldiers 

 by flies that shortly before had visited infected latrines. 



The bacillus is also occasionally present upon green vege- 

 tables grown in soil fertilized with infected human excre- 

 ment or sprinkled with polluted water, and epidemics are 

 reported in which the occurrence of the disease was traced 

 to oysters infected through sewage. NewsholmeJ found 

 that in 56 cases of typhoid fever about one-third were at- 

 tributable to eating raw shell-fish from sewage-polluted beds. 



Pathogenesis. The primary activities of the typhoid 

 bacillus are unknown. It is supposed that it passes uninjured 

 through the acid secretions of the stomach to enter the intes- 

 tine, where local disturbances are set up. Whether dur- 

 ing an early residence in the intestine its metabolism is 

 accompanied by the formation of a toxic product, irritating 

 to the mucosa, and affording the bacilli means of entrance 

 to the lymph-vessels, through diminutive breaches of con- 

 tinuity, is not known. We usually find it well established 

 in the intestinal and mesenteric lymphatics at the time we 

 are able to recognize the disease, though in rare cases it 

 appears able to reach the blood through other than the 

 customary channels and occasion an entirely different 

 pathologic picture. 



It is quite certain that the chief operations of the typhoid 



* "Hygienic Laboratory Bulletin No. 33," Washington, D. C., 1907. 

 t "Report on Typhoid Fever in the U. S. Military Camps in the Span- 

 ish War," vol. I. 



J"Brit. Med. Jour.," Jan. 1895. 



