PATHOGENIC ACTION OF B. COLL 341 



he could, to a certain extent, protect other animals against 

 the subsequent injection of virulent living typhoid bacilli. 

 On trying to use the agent in a curative way, i.e., injecting 

 it only after the bacilli had begun to produce their effects, 

 he got little or no result. 



There is thus evidence that the serum of persons who 

 have recovered from typhoid fever, and the serum of 

 animals artificially immunised against virulent typhoid 

 bacilli, protect from these bacilli. There is no evidence 

 that the serum has much power in neutralising the products 

 of these bacilli. We have thus this curious fact. Animals 

 are immunised by injections of the toxines of a bacillus ; 

 their serum, however, has no effect in neutralising its 

 toxines, but only aids in the destruction of the bacilli 

 which produce the toxines. Similar results have been 

 obtained in the case of cholera. 



The Pathogenicity of the B. coli and its Relation to that of the 

 Typhoid Bacillus. We have already seen that the B. coli is probably 

 responsible for the occurrence of some of the abscesses which follow 

 typhoid fever. It is also apparently the cause of some cases of summer 

 diarrhosa (cholera nostras), and of infantile diarrhoea. Its numbers in 

 the intestine are greatly increased during typhoid fever, and also during 

 any pathological condition affecting the intestine. Intraperitoneal 

 injection in guinea-pigs is occasionally fatal. Subcutaneous injection 

 results in local abscesses, and sometimes in death from cachexia. 

 Sanarelli found that the B. coli isolated from typhoid stools was much 

 more virulent than when isolated from the stools of healthy persons. 

 He holds that the increase in virulence is due to the effect of the 

 typhoid toxines, and devised an ingenious experiment which seems to 

 prove this point. This increased virulence of the B. coli in the typhoid 

 intestine makes it possible that some of the pathological changes in 

 typhoid may be due, not to the typhoid bacillus, but to the B. coli. 

 Some of the general symptoms may be intensified by the absorption of 

 toxic products formed by it and by other organisms. The question has 

 been raised as to whether the lesions produced in guinea-pigs by such 

 virulent B. coli can be distinguished from those of the B. typhosus. 

 Sanarelli holds that they can, and that the former partake more of the 

 nature of a septicaemia with pleurisy, pericarditis, and peritonitis ; 

 while in the latter the disease is more concentrated in the lymphatic 

 tissue of the intestine. He admits, however, that the differences are 

 more in degree than kind. Differences of behaviour of the two bacilli 

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



