BACILLUS TYPHUS US. 433 



subjects dead of this disease. The typhoid bacilli were 

 not only obtained from the spleen of the animal by 

 culture method, but the characteristic clumps were also 

 demonstrated microscopically in sections of the organ. 



It must be said, however, that such results are ex- 

 tremely rare. As a rule, the only effects that follow 

 the introduction of this organism into animals are refer- 

 able to the intoxicating action of the materials used. 

 In fact, the results of modern investigations have placed 

 bacillus typhosus in the category of toxin-producers, 

 and through the use of the toxins produced by it ani- 

 mals have been rendered immune from otherwise fatal 

 doses. The serum of such animals has also been shown 

 to possess a certain degree of immunizing power. 1 



In connection with the inoculation of animals with 

 bacillus typhosus observations of a most important 

 nature have been made by Sanarelli 2 upon the arti- 

 ficial induction of susceptibility to its pathogenic ac- 

 tion. He found that rabbits, guinea-pigs, and mice 

 could be rendered susceptible to infection by this organ- 

 ism by preliminary injections into them of the products 

 of growth of certain saprophytes bacillus vulgaris, 

 bacillus prodigiosus, and bacillus coli; and that by 

 whatever means the animal was subsequently inocu- 

 lated with fresh cultures of the typhoid bacillus, either 

 into the circulation or into the peritoneal cavity, death 

 resulted in from twelve to forty-eight hours, with 

 the pathological alterations most conspicuous in the 

 digestive tract, and particularly in the small intestine. 

 In these cases the infection is general, and the organisms 



1 Pfeiffer and Kolle : Zeitschrift fur Hygiene und Infektionskrank- 

 heiten, 1896, Bd. xxi. S. 208. 



2 Sanarelli: Annales de 1'Institut Pasteur, 1892, tome vi. 



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