160 THE UNIVERSITY SCIENCE BULLETIN. 



growth on agar slants, made it seem advisable to consider this 

 organism one of those unclassified, irregular organisms which are 

 not infrequently isolated from stools, although in many respects this 

 does not differ any more radically than irregular strains reported 

 by other observers. 



In running Widals in this laboratory it was customary to set up 

 each serum with B. typhosus, para A and para B. A member of the 

 department suggested that it might be advisable to use ' several 

 strains of B. typhosus in setting up routine Widals. Accordingly, a 

 Widal giving negative with the strain used. No. 2, was again set 

 up, using three other strains of typhoid. It again gave a negative 

 with No. 2, but was strongly positive with the other two strains. 

 It was recognized that apparent antigenic differences of this sort 

 might constitute an important source of error in making routine 

 laboratory tests. 



The sera for the Widals were obtained from various sources. 

 Sera A, C, D, F, G, J and I were from clinical cases of typhoid 

 from which the organism was subsequently isolated. The others 

 came as positive Widals from reputable laboratories, the majority 

 of which use the Rawlings strain. Most of the specimens were 

 drops of blood dried on a metal slide or on filter paper. A dilution 

 of 1-25 and 1-50 was made and an equal amount of a living sus- 

 pension of the organism was added, making an ultimate dilution 

 of 1-50 and 1-100. All Widals were set up using Nos. 1, 2, 3, 10 

 and 12. No. 12 was selected because it is the Rawlings strain and 

 is used for the army vaccine. Numbers 2 and 3 were used because 

 of the irregularities exhibited in the absorption tests and No. 10 

 because it was an organism giving a clear adherent agglutination 

 with most sera used. The results of these tests may be seen in 

 table VI. 



It was noticed that fresh serum drawn from the clot and used 

 within twenty-four or forty-eight hours gave positive agglutination 

 with a larger number of organisms than those made from dried 

 blood. In those Widals run with dried blood precipitation was 

 usually marked in the tubes giving a positive Widal. This might 

 be due to the presence of hemoglobin, foreign substances on the 

 metal slides or paper, some change in reaction, or some biochemical 

 change. This phenomenon is being investigated. No JDrecipitation 

 was noted in the Widals using clear serum, nor in the agglutination 

 tests with rabbit serum. Stober (14) mentions the occurrence of 

 both precipitation and agglutination with his immune sera. 



