ERADICATION OF PULLORUM DISEASE 1931-32 5 



was prepared and diluted to a turbidity equal to tube No. 1 of the McFarland 

 nephelometer. One-third had sufficient sodium hydroxide added to raise the 

 pH to 8.4. The other two-thirds were stored with the pH at 7.2. Both portions 

 were tested the day they were prepared and diluted. At later tests, these two 

 antigens and a third, produced by adding N/20 sodium hydroxide to raise the 

 pH to 8.4 to a portion taken from the stock of antigen of pH 7.2, were tested 

 with 5 positive and 5 negative sera. Tests were made each day for 8 days, then 

 at 10, 12, 14, 17, and 21 days of age, and each week to the conclusion of the 

 experiment. Whenever tests were made the pH and turbidity of each of the 

 stored portions of test fluid were determined. 



Table 1. — Results of Comparative Tests With Stored and Freshly Prepared 

 Antigens 



No. Value of Recorded More 



of Reaction of Sensitive 



Test All Sera Antigen 



Positive Serum Number of Negative 

 Reactions Sera Reacting 



Higher Identical Both S. F. 



only only 



* S — Stored antigen. F — Freshly prepared antigen. 



The remainder of the reactions of the ten positive sera were recorded as unsatisfactory. 



