120 STUDY AND IDENTIFICATION OF BACTERIA 



The colonies look like grapevine leaves. 



Growth on potato was also considered as affording information. At present, 

 the biochemical reactions give us information assisting in differentiation, and the 

 agglutination and bacteriolytic phenomena, the final diagnosis. The various plating 

 media are considered under media for plating out faeces. 



Not only do we find hyperplasia of the endothelial cells in the lymphoid tissue 

 of Peyer's patches and the mesenteric glands and the spleen, with subsequent necro- 

 ses, but focal necroses of the same character are found in the liver. 



A striking feature of the pathology of typhoid fever is the long-con- 

 tinued persistence of the organisms in the gall-bladder and elsewhere. 

 It is beginning to be believed that a previous typhoid infection, pos- 

 sibly so mild as to have passed unnoticed, is at the basis of gall-bladder 

 infections and resulting gall-stones. Various bone infections, especially 



FIG. 34. Seventy-two-hour-old culture of typhoid bacillus on gelatin. (Kolle and 



Wassermann.) 



osteomyelitis, have shown the typhoid bacilli in pure culture. For- 

 merly it was supposed that the typhoid bacillus brought about its lesions 

 by a local infection centered in the ileum. The present view is that 

 typhoid bacilli effect an entrance into the blood stream through some 

 lymphoid channel, as by tonsil or other alimentary lymphoid structure. 

 Of animals, only the chimpanzee seems to be susceptible. 



They develop in the general lymphatic system, the spleen in partic- 

 ular, where they are protected from the bactericidal power of the blood. 

 After a time, however, approximately the period of incubation, they 

 become so abundant in these lymphatic organs that they are carried 

 over into the general circulation. Then as a result of bacteriolysis the 

 intracellular toxins are liberated and symptoms develop. If bacteri- 



