342 TYPHOID FEVER. 



ward as confirmatory of the fact of their being distinct species. Thus 

 Sanarelli accustomed the intestinal mucous membrane of guinea-pigs 

 to toxines derived from an old culture of the B. coli, by introducing 

 day by day small quantities of the latter into the stomach. When a 

 relatively large dose could be tolerated, it was found that the introduc- 

 tion in the same way of a small quantity of typhoid toxine was followed 

 by fatal result. Pfeiffer also found that while the serum of conval- 

 escents from typhoid paralysed the typhoid bacilli, it had no more 

 effect on similar numbers of B. coli than the serum of healthy men. 



General View of the Relationship of the B. typhosus to 

 Typhoid Fever. i. We have in typhoid fever a disease 

 having its centre in and about the intestine, and acting 

 secondarily on many other parts of the body. In the 

 parts most affected there is always a bacillus present, 

 microscopically resembling other bacilli, especially the B. 

 coli, which is a normal inhabitant of the animal intestine. 

 This bacillus can be isolated from the characteristic lesions 

 of the disease and from other parts of the body as de- 

 scribed, and further, it is found by culture reactions to 

 differ from the B. coli. The whole series of culture 

 reactions, however, must be investigated before a particular 

 bacillus is identified as the B. typhosus, and no weight 

 must be attached to any observations made on the subject 

 when this has not been done. Here the important point, 

 however, is that a bacillus giving all the reactions of the 

 typhoid bacillus has never been isolated except from cases 

 of typhoid fever, or under circumstances that make it 

 possible for the bacillus in question to have been derived 

 from a case of typhoid fever. There is no evidence that 

 the B. coli can be transformed into the typhoid bacillus, or 

 the typhoid bacillus into the B. coli, though of course this 

 does not preclude the possibility of the one having been 

 originally derived from the other. All practically are now 

 agreed that two separate bacilli exist, the B. coli and the 

 B. typhosus. 



2. Against the etiological relationship of the latter to 

 the disease several facts may be adduced. First, there is 

 the comparative difficulty of the isolation of the B. typhosus 

 from the stools of typhoid patients. We have pointed out, 



