340 TYPHOID FEVER. 



an otherwise fatal dose of the original living virulent cul- 

 ture. The experiments were repeated on guinea-pigs with 

 a similar result, and it was also found that the serum of a 

 guinea-pig thus immunised could, if transferred to another 

 guinea-pig, protect the latter from the subsequent injection 

 of a dose of typhoid bacilli to which it would naturally suc- 

 cumb. 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 sub- 

 cutaneous doses of typhoid cultures in bouillon, in which 

 the bacilli had been killed by heat or chloroform vapour. 

 Experiments performed with serum derived from typhoid 

 patients and convalescents have been adduced as bearing 

 on the matter. Many observers had noticed that the 

 serum of men convalescent from typhoid had an inimical 

 effect on typhoid bacilli ; and these results have been con- 

 firmed by PfeifTer, whose technique was less open to 

 objection than that of most previous workers. He found 

 that the serum of healthy men had such an action but in a 

 much less degree. The method was to mix the serum and 

 the bacilli in a little bouillon, and inject the whole intra- 

 peritoneally into guinea-pigs. He found that when the 

 latter did not die, the bacilli became motionless and ap- 

 parently dead, and that plate cultures made after a time 

 from the exudation containing them, remained sterile. The 

 serum of such patients has, therefore, antimicrobic powers, 

 but there is no evidence that it contains any antitoxic 

 bodies (see chapter on Immunity). Pfeiffer, for example, 

 found that on adding serum from typhoid convalescents to 

 the typhoid toxines, and injecting the mixture into guinea- 

 pigs, death took place as in control animals which had 

 received the toxines alone. Sanarelli also found that while 

 the injection of toxines obtained as above described, 

 rendered the animal immune to a certain dose of living 

 bacilli, it still could be killed by a further dose of the 

 toxine. He does not, however, give the doses employed. 

 Pfeiffer found that by using the serum of immunised goats 



