EXPERIMENT STATION REPORTS. 199 



SUMMARY. 



There does not appear to be auy iudividual difference in tlie agglutiua- 

 bility of 21 strains of Bact. abortus procured from different parts of this 

 country and Europe. Taking the agglutination results on fifteen sera 

 as a criterion, there does not appear to be any difference in the type 

 of Bact. abortus which invades the tissues of animals in different dis- 

 tricts of this country. 



• 



Bibliography. 



1. Fusier, M. L., and Meyer, K. F., 



Principles in serologic grouping of B. abortus and B. melitensis. 

 Correlation between absorption and agglutination tests. Jour. 

 Inf. Dis., Vol. 27, p. 185, 1922. 



2. Huddleson, I. F., 



The comparative patliogenicity of several strains of Bact. abortus 

 (Bang). Mich. Agr. Exp. Sta. Technical Bulletin 55, March, 

 1922. 



Tlic Influcnm of Different Preservatives on the Agglutinability of 



Bact. abortus. 



It is of considerable practical importance that the sensitivity of the 

 agglutination test for the diagnosis of infectious abortion should be 

 fully developed. In view of the fact that the addition of foreign agents 

 or nuiterial may affect the agglutinability of the antigen, the influence 

 of different preservatives such as phenol, tricresol, ether, formalin and 

 no preservative are herein considered. 



The antigen was prepared in the manner previously described and 

 suspended in physiological salt solution. To a series of suspensions 

 were added phenol to 0.5 percent, tricresol to 0.1 per cent, formalin to 

 0.5 per cent and ether to 0.5 per cent. The antigens were placed in the 

 ice-box for 24 hours before using. 



The 28 sera used represent a small number of sera sent to the laboratory 

 for diagnosis. They were used unheated owing to the fact that we have 

 found that serum agglutinins, as shown in Table II, are partially or 

 totally destroyed in many cases when heated at 56° C. for thirty minutes. 



The agglutination tests were conducted as previously described. 



Table I illustrates the effects of the different preservatives on the 

 reaction. The slight degree of difference represented here between 

 antigens containing phenol, formalin and ether is within the limit of 

 experimental error and should not be considered. There is a marked 

 influence on the agglutinability of the antigen preserved with tricresol 

 to the extent of inhibiting clumping completely or causing zone aggluti- 

 nation. Formalin should not be used in the antigen in a greater con- 

 centration than given here as it will also inhibit clumping in many 

 cases, but not in all. Comparative tests with fresh unheated and heated 

 (56° C. for 30 minutes) antigens and those preserved with phenol, for- 

 malin or ether showed no increased sensitivity in favor of the unpre- 

 served antigens. 



