846 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



colored macules or spots which may be few or numerous and occur in 

 successive crops. During the third week in mild cases these symptoms 

 gradually subside. In severer forms no abatement is shown and com- 

 plications are liable to occur. The fourth week shows beginning 

 convalescence in the typical case. 



The characteristic pathological findings are swelling and ulceration 

 of the lymphoid structures of the lower part of the small intestine best 

 seen in the Peyer's patches of the ileum just above the ileo-cecal valve. 

 The mesenteric glands and spleen are hyperaemic. Parenchymatous 

 degenerations more or less severe may be found in other organs. The 

 characteristic histological feature is the crowding of the lymph spaces 

 by proliferated endothelial cells. 



Perforation and hemorrhage of the bowel, peritonitis, myocarditis, 

 thrombosis, etc., render typhoid fever a dangerous disease. The fatality 

 varies considerably; at one time estimated at 25 per cent, it has been 

 brought down to 10 to 15 per cent by modern methods of treatment 

 and has been given in Minnesota as low as 4 per cent. 



Eberth found the organism in 1880 by the examination of the 

 mesenteric glands and spleen of fatal cases. Gaffky cultivated it in 

 1884. The causal relationship has been a matter of gradual acceptance 

 through evidence furnished by the study of such immunity processes 

 as agglutination, bacteriolysis, and complement deviation, and finally 

 by the high percentage of positive blood cultures. Conclusive evidence 

 is afforded by the development of typhoid fever following the ingestion 

 of pure cultures with suicidal intent. 



The agglutination reaction of Gruber and Widal is universally 

 employed in diagnostic laboratories. The blood serum of typhoid 

 patients, after a certain period of the disease, will cause a characteristic 

 clumping of the bacilli when mixed with pure cultures. The fresh 

 serum from a clot may be used, or, more conveniently, dried blood 

 from which a watery extract can be made. In positive cases the reac- 

 tion is present in at least the one-fiftieth dilution and usually in the one- 

 hundredth or higher dilutions. The culture employed should be 

 eighteen to twenty-four hours old; it should be freely agglutinable and 

 show no artificial clumping, characters not possessed by all strains, 

 especially those recently isolated. Cultures killed by a small per- 

 centage of carbolic acid have been recommended for constancy in place 



