346 TYPHOID FEVER. 



concerned, as it is probable that all the forms which these take 

 in man have not been recognised. The very wide application 

 of the reaction has elicited the fact that it is given in many cases 

 of slight, transient, and ill-defined febriculae, which occur espe- 

 cially 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 say 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 im- 

 munisation 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 sloped agar culture when administered hypo- 

 dermically will kill a guinea-pig of from 350 to 400 grammes. 

 Vaccination can be accomplished by emulsifying such a culture 

 in bouillon, and killing it by heating for five minutes at 60° C. 

 For use, from one-twentieth to one-fourth of the dead culture is 

 injected hypodermically, usually in the flank. The vaccine now 

 sent out by Wright, however, consists of a portion of a bouillon 

 culture similarly treated. The effects of the injection are some 

 tenderness locally and in the adjacent lymphatic glands, and it 

 may be local swelling, all of which come on in a few hours, and 

 may be accompanied by a general feeling of restlessness and a 

 rise of temperature, but the illness is over in twenty-four hours. 

 During the next ten days the blood of the individual begins to 

 manifest, when tested, a positive Widal's reaction, and further, 

 Wright has found that usually after the injection there is a 

 marked increase in the capacity of the blood serum to kill the 

 typhoid bacilli in vitro. There is little doubt that these observa- 

 tions indicate that the vaccinated person possesses a degree of 

 immunity against the bacillus, and this conclusion is borne out 

 by the results obtained in the use of the vaccine as a prophy- 

 lactic against typhoid fever. Extensive observations have been 

 made in. the British army in India, and also in the South African 



