446 INFECTION AND IMMUNITY. 



next day his temperature comes down to normal, 

 and he feels comparatively well except in respect 

 to pain at the seat of inoculation." Of 5,473 sol- 

 diers vaccinated against typhoid, twenty-one took 

 the disease and two died. In 6,610 soldiers under 

 similar conditions who were not vaccinated, there 

 were 187 cases and twenty-six deaths (Leish- 

 mann). The method of vaccination used by Kus- 

 sell and his associates in the U. S. Army is similar 

 to that of Wright, but three injections ten days 

 apart are given, the first of 500 million, the second 

 and third of one billion. No bad results have 

 occurred in 8,510 cases, and the results have been 

 satisfactory, not a single case of typhoid occurring 

 in any one whose vaccination was completed. 

 Among the unprotected in the army 200 cases 

 developed in the same period of time. 



The vaccine was prepared as follows: A non- 

 virulent strain of the bacillus is grown on agar, 

 slanted in flasks for twenty-four hours. The 

 growth is then emulsified in salt solution and 

 standardized to contain 1 billion bacilli to 1 c.c. 



The vaccine is then sterilized by heating to 56 

 C. for one hour; 0.25 per cent, tricresol is added 

 as a preservative and the sterility tested by aerobic 

 and anaerobic cultures. The harmlessness is proved 

 by inoculation into guinea-pigs and mice. 

 conditions The adoption of antityphoid inoculation or vac- 

 vaccination* cination under certain conditions appears to be 

 warranted. Typhoid never has been a world pest; 

 but in the presence of epidemics in densely popu- 

 lated districts, the method may well be considered. 

 The question is a pertinent one also for those cities 

 in which typhoid is so extensive as to be called 

 endemic. It has a distinct field in the protection 



