162 THE UNIVERSITY SCIENCE BULLETIN. 



From table VI it is readily seen that different organisms with the 

 same sera set up at the time showed marked differences in agglutin- 

 ability. This may be due to the different agglutinabilities inherent 

 in the organisms themselves and such marked differences probably 

 would not be noted had absorption tests been possible. It is 

 recognized that these twenty positive Widals are too few to provide 

 a basis for accurate conclusions. It seems highly probable that the 

 dried-blood method exaggerates the antigenic differences between 

 the organisms, changing what is probably a quantitative into an 

 apparently qualitative difference between the organisms. The low 

 percentage of positives given with Nos. 2 and 3 might be expected 

 from the results given in the absorption tests using immune sera. 

 No. 10, on the other hand, gave a very low percentage of negatives. 

 Those read as partial agglutination in clinical work would be called 

 positive. The tubes read as positive gave complete clearing of the 

 supernatant fluid ; those read as partial agglutination showed unmis- 

 takable agglutination, but with some cloudiness of the supernatant 

 fluid. No. 10, therefore, gave 93 per cent positive. No. 12, while giv- 

 ing the highest percentage of complete agglutinations, gave only 90 

 per cent positive when partial agglutinations are included. It seems 

 probable in view of the results obtained that it might be worth while 

 to use more than one strain of typhoid in running Widals and to 

 select easily agglutinable strains, such as No. 10 Mt. Sinai strain, 

 and No. 12 the Rawlings strain. 



The serological reactions here recorded might have an important 

 bearing on the following points: 



1. The occurrence of typhoid fever in vaccinated persons. 



2. The advisability of using a polyvalent vaccine. 



3. The occurrence of negative Widals in clinical cases of typhoid 

 fever. 



4. Sources of error due to the dried-blood method. 



A number of cases o,f typhoid fever occurring in vaccinated in- 

 dividuals may be found in the literature. Vaughn (10) says that 

 "It is possible that in so far as vaccination has failed it is due to 

 the disease being caused by other members of the typhoid group, 

 . . . which in all probability is much larger than we now ap- 

 preciate." Mock (11) reports the occurrence of forty-five cases of 

 typhoid and paratyphoid in individuals who had been vaccinated 

 about one year previous to the attack. Some of the strains isolated 

 were atypical in regard to their cultural and serological reactions, 

 but were identified positively as typhoid or paratyphoid organisms. 



