182 TYPHOID FEVER. 



Diagnostic Values. If the reaction is present, but not well 

 marked, only probable diagnosis may be made. If the reac- 

 tion is absent in a patient sick seven days, the diagnosis of 

 typhoid fever may be excluded. The agglutination reaction 

 is capable of manifestation macroscopically, even with killed 

 bacteria, and many preparations and methods of their use are 

 in vogue. Their advantage, of course, lies in their stability 

 and lack of dangerousness, but with the availability of free 

 board-of-health laboratories, whence returns may be received 

 in twenty-four to forty-eight hours, it would seem that even in 

 the remotest communities the promiscuous use by general 

 practitioners of these various " diagnostica " would mean the 

 needless sacrifice of accuracy to haste. 



Vaccination Against Typhoid Fever. 



Wright and Semple have recently practised the vaccination 

 of human beings against typhoid fever, and extensive ob- 

 servations have been made in India and South Africa in the 

 British Army. For this purpose a typhoid vaccine consisting 

 of a bouillon emulsion made from a slant agar culture of the 

 Bacillus typhosus twenty-four hours old is used. The cult- 

 ure is killed by heating it for five minutes at a temperature 

 of 60 C. From a half to a quarter of the whole culture 

 is used for one vaccination, and the culture must be of such 

 a strength that a fourth of it is capable of killing a 300- 

 to 400-gram guinea-pig, when the same is injected into it, 

 without killing the bacilli. Similar injections of vaccines have 

 been practised by the Germans in East Africa. The United 

 States government has given its approval to this method. 

 The recruits in nearly all the armies of the world receive the 

 preventive inoculation. Nurses and physicians exposed to 

 infection take advantage of the method. The usual dose of 

 the first injection is 500,000,000 dead B. typhosus. At the 

 end of the first and second weeks injections of double this 

 amount are given. As the favorable reports of the active 

 immunity produced from all over the world cover several 

 hundred thousand cases, this method of preventive inocula- 



