RELATION OF B. TYPHOSUS TO TYPHOID. 339 



may be intensified by the absorption of toxic products formed by it and by other 

 organisms. It is to be noted that lesions produced in guinea-pigs are very 

 similar to those of the B. typhosus. Differences of behaviour of the two 

 bacilli, in connection with their pathological effects, have been brought for- 

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

 accustomed the intestinal mucous membrane of guinea-pigs to toxins 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 introduction in the same way of a small quantity of typhoid 

 toxin was followed by fatal result. Pfeiffer also found that while the serum of 

 convalescents 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 charac- 

 teristic lesions of the disease and from other parts of the body 

 as described, 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 circum- 

 stances 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 com- 

 parative difficulty of the isolation of the B. typhosus from the 

 stools of typhoid patients. We have pointed out, however, that 

 the latter can be isolated during the first ten days of the disease, 

 and that the extraordinary multiplication of the B. coli, which 

 takes place in any pathological condition of the intestine, 



