METHODS AND CONTROLS 



35 



hours at 52 C. The end-point was taken as the highest dilution 

 at which distinct clumping could be seen by holding the tube 

 against a dark background. 



MICROSCOPIC METHOD 



Dilutions were made as for the macroscopic method. One 

 loopful of the diluted serum was mixed with one loopful of the 

 suspension of the organism on a cover-slip which was inverted 

 over a hollow slide and incubated for fifteen minutes at 37 C. 



From time to time control agglutination tests were done with 

 sera from normal individuals, some of whom had received pre- 

 ventive inoculations with vaccines of B. typhosus, B. para- 

 typhosus, A and B (indicated T, A, B in tables). Control tests 

 were also done with the Metz and Syrie Proteus cultures, B. 

 typhosus, B. paratyphosus, A and B, using stock immune sera 

 for B. typhosus, B. paratyphosus A, and B. paratyphosus B. 

 The results of these controls are shown in Tables IV to VI on 

 pp. 35 and 36. 



In addition to the controls tabulated, controls were done 

 with each series of Weil-Felix tests. One tube containing the 

 saline suspension of each culture plus normal salt solution and 

 one tube containing normal human serum (No. 1 in the tables) 

 diluted 1-50 were set up and incubated. These controls were 

 negative in each instance. 



2. TABULATION OF CONTROLS (Done by macroscopic 



method) 



TABLE IV. TESTS DONE ON NORMAL SERA BEFORE 

 BEGINNING WORK 



For footnote, see p. 36. 



