MICROBIAL DISEASES OP MAN AND DOMESTIC ANIMALS 793 



The period of incubation varies ordinarily from five to twenty-one 

 days, with an average of fourteen days. 



The first week of the disease in man begins with a train of rather 

 indefinite symptoms such as headache, loss of appetite, digestive dis- 

 turbances, lassitude, and sleeplessness. Nose bleed is a peculiar and 

 rather constant feature. The temperature and pulse gradually rise 

 until by the end of five to seven days the former has become high, 

 i03°F. to io4°F. and constant. The temperature continues thus 

 through the second week during which a gradual stupor and occasional 

 deUrium, diarrhoea, and enlargement of the spleen occur. The pulse is 

 often dicrotic and there is a rash consisting of isolated flattened rose- 

 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 shovm and com- 

 plications are liable to occur. The fourth week shows beginning 

 convalescence in the tj^ical case. 



The characteristic pathological findings are swelling and ulceration 

 of the Ijmiphoid 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 pgsitive 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 



