VACCINATION AGAINST TYPHOID 343 



such precautions be adopted the absorption method can be util- 

 ised for the differentiation of the typhoid and paratyphoid organ- 

 isms and their infections and for similar investigations. 



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 such a culture emulsified 

 in bouillon, and killed 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 

 used, however, actually 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, an agglutination 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 bacillus 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 in the South African 

 War the efficacy of the treatment was put to test. Though 

 in isolated cases not much difference was observed among 

 those treated as compared with those untreated, yet the broad 

 general result may be said to leave little doubt that on the 

 one hand protective inoculation diminishes the tendency for the 

 individual to contract typhoid fever, and on the other, if the 

 disease be contracted, the likelihood of its having a fatal result 

 is diminished. Thus in India of 4502 soldiers inoculated, *98 

 per cent contracted typhoid, while of 25,851 soldiers in the 

 same stations who were not inoculated, 2*54 per cent took the 

 disease. In Ladysmith during the siege there were 1705 

 soldiers inoculated, among whom 2 per cent of cases occurred, 

 and 10,529 uninoculated, among whom 14 per cent suffered 

 from typhoid. Wright has collected statistics dealing in all 

 with 49,600 individuals, of whom 8600 were inoculated, and 



