PATHOGENICITY OF B. COLI 333 



which it would naturally succumb. Chantemesse and Widal, 

 Sanarelli, and also Pfeiffer, succeeded in immunising guinea-pigs 

 against the subsequent intraperitoneal injection of virulent 

 living typhoid bacilli, by repeated and gradually increasing 

 intraperitoneal or subcutaneous doses of dead typhoid cultures 

 in bouillon. Experiments performed with serum derived from 

 typhoid patients and convalescents indicate that similar effects 

 occur in those who have successfully resisted the natural disease. 

 The serum of such patients has antibacterial powers, but 

 there is no evidence that it contains any antitoxic bodies (see 

 chapter on Immunity). Pfeiffer, for example, found on adding 

 serum from typhoid convalescents to the bodies of typhoid 

 bacilli killed by heat, and injecting the mixture into guinea- 

 pigs, that death took place as in control animals which had 

 received these toxic agents alone. Pfeiffer also found that by 

 using the serum of immunised goats, 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. 



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 

 diarrhoea (cholera nostras), of infantile diarrhcea, and of some food 

 poisonings. 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 often fatal. Sub- 

 cutaneous injection may result 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 typhoid toxins. 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. 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 forward 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 still 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. 



