TYPHOID BACILLUS 329 



Typhoid Fever. Pathogenesis. Experimental Typhoid fever is a 

 disease of man only, and until recently rigorous experimental proof 

 that the typhoid bacillus is the specific cause of this infection has been 

 lacking. The evidence of the etiological relationship of the typhoid 

 bacillus is of two kinds: (1) a few cases where laboratory attendants 

 have accidentally or purposely swallowed cultures of typhoid fever 

 and have developed the disease ; (2) experiments of Metchnikoff and 

 Besredka. 1 



The experiments of Metchnikoff and Besredka appear to be con- 

 clusive. They produced typhoid fever in anthropoid apes by feeding 

 the animal food infected with fecal material containing typhoid bacilli. 

 The animals (fifteen in all) developed fever and diarrhea after eight 

 days, and typhoid bacilli were isolated from the blood stream on the 

 tenth day. Three died. Specific agglutinins were demonstrable in 

 the blood serum, and the clinical picture was essentially that of typical 

 typhoid fever. These observers ruled out the possibility of a filterable 

 virus. 



Pathogenesis in Man. Portal of Entry. Typhoid bacilli enter the 

 body through the mouth and pass through the gastro-intestinal tract. 

 They lodge in lymphatic tissue of the intestines, particularly Peyer's 

 patches, then invade the general lymphatic system and spleen, and 

 are found in the blood, especially during the first week of the clinical 

 disease. Typhoid fever, therefore, is a bacteremia. Rose spots, which 

 are frequently found on the abdomen during the first week of the 

 clinical disease, contain colonies of typhoid bacilli which are localized 

 in the subcutaneous tissue. 2 Characteristic lesions are found in Peyer's 

 patches which at first are swollen and hyperemic. After a few days 

 the glands become rather pale, caused, in part at least, by hyperplasia 

 of the lymphoid and endothelioid cells, which cuts off the blood supply 

 in whole or in part, leaving these areas even more prominent (medul- 

 lary swelling). 3 Necrosis then commences and the glands gradually 

 become yellowish in color and 'softer in consistency. Soon the necrosis 

 ceases rather abruptly as immunity checks the process and the necrotic 

 tissue then sloughs away, leaving a somewhat irregular elongated ulcer 

 which usually extends to or through the muscular layer of the intestine. 

 About the end of the third week scar tissue begins to appear in these 

 ulcers, which in time practically fills up the original area, leaving the 



1 Ann. Inst. Past., March 25, 1911; xxv, 193, 865. 



2 Richardson, Philadelphia Med. Jour., March, 1900. (Special Typhoid Fever Number.) 

 8 Mallory, Jour. Exp. Med., 1898, iii, No. 6, p. 611. 



