INTRODUCTORY
Prophylactic immunization against typhoid fever offers sufficient security against subsequent infection to render its general application advocable. Such application is not only becoming wide-spread and mandatory in segregated, controllable bodies like armies, but has proved very advantageous in communities in general. In surveying the already extensive statistical literature, one becomes convinced of the relative protection against typhoid fever that is enjoyed by those who have been immunized with preparations of the typhoid bacillus; one is likewise convinced that the results obtained and the methods of immunization followed leave much to be desired.Why should the results of immunization against typhoid infection be less perfect than those obtained in small-pox and rabies? Why should artificial immunization with the typhoid bacillus offer so much less perfect protection than recovery from typhoid fever ? In respect to the method employed we may well question why 500,000,000 killed typhoid bacilli