ERADICATION OF PULLORUM DISEASE 1931-32 9 



at 8 ° C. and the other two held at room temperature. Of the two at room tem- 

 perature, one set was chosen to be transferred each week and the other once a 

 month when each of the sets was transferred to duphcate agar slants as the 

 first step in the preparation of antigen. After 24 hours' incubation, one of these 

 was returned to its place of storage and the other used to inoculate the medium 

 from which the growth was washed as antigen. From the three antigens pre- 

 pared, tests were made with 5 positive and 5 negative sera. The antigen from the 

 control cultures served as a standard of comparison for each of the other two 

 antigens. |^* 



Graphs 2 and 3 show the relation of each antigen to the control antigen and 

 the degree of fluctuation more clearly than can be described. A summary of 

 the numerical deductions of the 11 different antigens prepared and tested is 

 given below: 



Comparative Results on Antigens Prepared from Cultures Retained at Different Storage 

 Temperatures 



A nligens prepared from cultures 

 stored at temperatures 

 8°C. 22° C. 



Number of tests 11 11 



Number of sera tested 110 110 



Total value of all reactions 1,222 1,213 



Number of positive sera tested 55 55 



Number of positive sera with higher value 20 20 



Number of positive sera with identical value 15 15 



Number of negative sera tested 55 55 



Number of negative sera reacting 15 19 



Total value of reactions in negative sera 26 33 



Number of tests more sensitive 7 4 



Comparative Results on Antigens Prepared from Cultures Transferred at Frequent 

 Intervals 



Antigens prepared from 



cultures transferred 

 Monthly Weekly 



Number of tests 11 11 



Number of sera tested 110 110 



Total value of all reactions 1,213 1,200 



Number of positive sera tested 55 55 



Number of positive sera with higher value 23 17 



Number of positive sera with identical value 15 15 



Number of negative sera tested 55 55 



Number of negative sera reacting 19 15 



Total value of reactions in negative sera 33 27 



Number of tests more sensitive 6 5 



Smears of the three sets of cultures were made and stained for microscopic 

 examination and comparison six times during the experiment. Slight variations 

 were observed, for the greater part, an irregularity in the size of the organism 

 in each strain and a tendency to form short chains in some cases. The variations 

 were similar for the cultures transferred frequently and for those held at 8° C. 



The type of agglutination reactions of the different antigens appeared almost 

 identical, comparing well with the degree of reactions from which the numerical 

 data were compiled. 



Conclusions 



1. Under the conditions of the investigation, concentrated 5. puUorutn 

 antigen remained as sensitive and specific after 583 days' storage at approxi- 

 mately 8 ° C. as freshly prepared antigen. 



