THE COLON, TYPHOID AND DYSENTERY BACILLI 333 



caused by feeding the organisms, with resulting lesions in the in- 

 testine, bacilli in the blood and spleen, and a continued fever. 



Typhoid fever exists generally throughout the temperate 

 zone, is present throughout the year but most prevalent in the 

 fall. The usual mode of infection is undoubtedly through food 

 and drink. The bacilli swallowed survive in part the action of 

 the gastric juice and so gain the lumen of the duodenum. The 

 first multiplication seems to occur here 1 in a location fairly free 

 from bacteria in health. The infection extends along the wall 

 of the intestine, involving especially the lymphatic structures, 

 solitary glands and Peyer's patches. The bacteria pass into 

 the lymph stream to be carried to the mesenteric nodes, spleen 

 and into the blood. At the onset of definite symptoms of typhoid 

 fever the bacilli have usually reached the general blood circu- 

 lation. Subsequently the infection reaches the gall bladder, per- 

 haps by extension along the common bile duct and cystic duct or 

 perhaps by the blood stream through the liver; the organisms 

 also pass through the kidney and multiply in the contents of the 

 urinary bladder. They are present in the rose spots on the 

 skin. The bacilli are often present in the feces in small numbers, 

 the abundance of other organisms making their isolation and 

 recognition difficult. At times localized inflammations due to 

 B. typhosus develop elsewhere in the body, as in the lungs. It 

 is evident therefore that the bacilli may leave the body of the 

 patient through many channels, but chiefly with the urine and 

 feces. Even after recovery the patient may continue to dis- 

 charge virulent bacilli for months or years. It is estimated that 

 one per cent of recovered cases are persistent carriers of the in- 

 fectious agent. 



The bacteriological diagnosis of typhoid fever depends upon 

 isolation and recognition of the germ or detection of specific sub- 

 stances in the blood produced by the patient as a reaction to the 

 presence of B. typhosus. B. typhosus is sought by blood culture 

 (see page 101) diluting the blood with large amounts of broth 

 1 Hess: Journ. Infect, Diseases, 1912, Vol. XI, pp. 71-76. 



