Pathogenesis 551 



micro-organisms. In their most useful and comprehensive 

 "Report upon the Origin and Prevalence of Typhoid Fever 

 in the District of Columbia," Rosenau, Lumsden, and 

 Kastle,* were able to connect 10 per cent, of the cases with 

 infection through milk. Interesting additional facts upon 

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

 laboratory upon "Milk in its Relation to the Public Health." 



The primary operations of the typhoid bacillus are 

 unknown. It is supposed that it passes uninjured through 

 the acid secretions of the stomach to enter the intestine, 

 where primary local disturbances are set up. Whether 

 during 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 

 bacillus are in the tissues and not in the intestine, as seems 

 to be a widely prevalent error. It is contrary to most of 

 our knowledge of the organism that it should easily adapt 

 itself to saprophytic existence among the more vigorous 

 intestinal organisms. Those who look for it in the feces 

 are usually surprised at the difficulty of finding it, or at the 

 small numbers they succeed in isolating. It is far more 

 easy to isolate the organism from the blood than from the 

 feces, and much greater numbers occur in the urine than in 

 the feces. It probably escapes from the blood into the 

 bile, where it grows luxuriantly, and entering the gall-bladder 

 may take up permanent residence there, escaping into the 

 intestine each time the gall-bladder is emptied. Such bacilli 

 as are thus discharged are probably destroyed in the intestine, 

 though in certain cases they escape destruction, so that some 

 convalescents from typhoid fever are for years distributing 

 bacilli in their feces. The failure to find them in the feces 

 in considerable numbers during the course of the disease 

 depends upon their absence in most cases after the febrile 

 stage of the disease is established, and not upon imperfection 



* "Hygienic Laboratory Bulletin No. 35," Washington, D. C., 1907. 



