TYPHOID BACILLUS 365 
and have developed the disease; (2) experiments of I\ letch nikoft" and 
Besredka.^ 
The experiments of ^Nletchnikoff and Besredka appear to be con- 
clusive. They produced typhoid fever in anthropoid apes by feeding 
the animals food infected with fecal material containing typhoid bacilli. 
These 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 filtrable 
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, grow 
there, and overflow into the blood, especially during the first week of 
the clinical disease. Typhoid fever, therefore, is a bacteriemia. 
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.^ 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 (medullary swelling) .^ 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 site of the 
ulcer marked by a somewhat depressed cicatrix. Occasionally second- 
ary infection of the ulcers results in perforation or hemorrhage, and 
sometimes an uninfected ulcer may erode through a bloodvessel 
causing hemorrhage. It should be remembered that typhoid lUcers 
tend to run along the kmg axis of the intestine, whereas tuberculous 
ulcers, on the contrary, run transversely, following the course of the 
lymphatics. 
In addition to the intestinal lesions, there is in typhoid fever an 
acute splenic tumor with a great proliferation of typhoid bacilli in 
this orsan. Foci of typhoid bacilli are commonly foimd also in the 
kidneys and the liver, mesenteric lymph nodes, less commonly in lungs, 
1 Ann. Inst. Pasteur, 1911, 25, 193, 865. 
2 Richardson: Philadelphia Med. Jour., March, 1900. (Special Tj-phoid Fever 
Number.) 
5 Mallory: Jour. Exp. Med., 1898, 3, 611, 
