126 THE ACUTE SELF-LIMITED INFECTIONS 



bacillus. The bacillus belongs to the so-called typho- 

 colon group (see p. 177). The lower animals do not 

 develop typhoid fever when inoculated with this germ, 

 but die of septicemia, usually with peritonitis. 



Immunization. An antitoxin to the typhoid bacillus 

 cannot be produced, but attempts at active immuni- 

 zation have been made with some success. These 

 attempts take the direction of injecting the bacilli 

 in such a form that they cannot produce the disease, 

 but yet set up some resistance to it comparable to that 

 acquired by passing through a spontaneous attack. 

 The bacilli are prepared like the vaccines or bacterins 

 described on p. 76, and injected under the skin. A 

 slight fever may result, but no further bad effects have 

 been noted. All symptoms are over in twenty-four 

 hours after each injection. The bacteria are intro- 

 duced three times in quantities of 500,000,000, 

 1,000,000,000 and 1,000,000,000 at ten-day intervals. 

 The immunity resulting is supposed to last about two 

 years. This vaccine method is well adapted for and 

 most used by armies going into camps. The results 

 in our army and that of Great Britian have been very 

 encouraging. It should be taken by nurses doing army 

 nursing or seeing many typhoid cases. 



Major Russell, U. S. A., concludes his investigations 

 into the theory and practice of antityphoid vaccination 

 as a prophylactic as follows: 



1. Antityphoid vaccination in healthy persons is a 

 harmless procedure. 



2. It confers almost absolute immunity against 

 infection. 



3. It is the principal cause of the immunity of our 

 troops against typhoid in the recent Texas maneuvers. 



