164 TYPHOID FEVER. 



The blood only of fever patients is to be used. Should the 

 report be negatived and the case be suspicious, the physician 

 in attendance is requested to send another specimen, and in 

 every case to notify the bacteriologist as to whether the labo- 

 ratory diagnosis is finally in harmony with the clinical diag- 

 nosis or at variance with it. 



Sources of Error. One, which must be remembered, is due 

 in some cases to the persistence of the reaction for a number 

 of years after a typhoid attack : so that a reaction may appear 

 in health or in aifections other than typhoid fever, if the 

 patient has previously suffered from the disease. In cases in 

 which the reaction is marked, it may apparently be positively 

 stated that the patient has, or has had, typhoid fever within 

 a few years. 



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 experiment has not been tried long enough and not in a 

 sufficient number of cases to permit a positive statement as to the 

 earliest date of the appearance of the reaction in typhoid fever. 



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. 



The results obtained by these vaccinations have been en- 

 couraging and seem to open up a promising field for the 

 serum-therapy of typhoid fever. 



