VACCINATION AGAINST TYPHOID 349 



of typhoid fever previously with persistence of agglutinative 

 capacity ; the case may be one of disease caused by an 

 allied bacillus ; the disease may have a quite different 

 cause, and yet the serum may react with typhoid bacilli ; 

 the disease may be typhoid fever and yet no reaction may 

 occur. The most important of these sources of error is that 

 with which diseases caused by allied organisms are concerned, 

 as it is probable that all the forms which these take in man 

 have not been recognised. The very wide application of 

 the Widal reaction has elicited the fact that it is given in 

 many cases of slight, transient and ill-defined febriculse, 

 which occur especially when typhoid fever is prevalent. 

 Our knowledge of these is still insufficient to justify our 

 setting all of them down as cases of aborted typhoid. 

 There is no doubt that, taking all the facts into account, 

 the cases where the reaction gives undoubtedly correct 

 information so far outnumber those in .which an error may 

 be made that it must be looked on as a most valuable 

 aid to diagnosis. In concluding we may point out here 

 that the fact of a typhoid serum clumping allied bacilli in 

 no way, so far as our present knowledge goes, justifies doubt 

 being cast on the specific relation of the typhoid bacillus 

 to typhoid fever. 



Vaccination against Typhoid. The principles of the 

 immunisation of animals against typhoid bacilli have been 

 applied by Wright and Semple to man in the following 

 way. Typhoid bacilli are obtained of such virulence that 

 a quarter of a twenty -four hours' old agar culture when 

 administered hypodermically will kill a guinea-pig of from 

 350 to 400 grammes. Such a culture is emulsified in 

 bouillon and killed by being raised to 60 C. and kept at 

 that for five minutes. . The vaccination is accomplished by 

 the hypodermic injection of from one-twentieth to one-fourth 

 of such a dead culture. The effects of such an injection 

 are some local tenderness, and it may be swelling, and a 

 general feeling of restlessness for some hours with occa- 

 sionally a slight rise of temperature. The possibility of 

 this vaccination preventing the development of typhoid 



