168 VETERINARY STATE BOARD 



and can be destroyed by heating the serum to 56° C. for half an 

 hour. (This is called inactivating the serum) ; the other substance, 

 known as the immune tody, hcemolytic amboceptor, or antibody. 

 By inactivating the serum, the power of haemolysis is lost, because 

 the complement is destroyed; but this power can be restored by 

 adding fresh serum which always contains complement. Guinea-pig 

 serum is very rich in complement and is used in the test. 



In horses affected with glanders, the infectious principle, the 

 toxin, stimulates the production of antibodies. These antibodies, 

 or bacterial amboceptors, are nature's fighters against the invading 

 toxin. For use in this test, this toxin is obtained by making an ex- 

 tract of an artificial growth of glanders bacilli, and is called antigen. 



If the serum of a glandered animal which, of course, contains 

 antibodies, is inactivated (complement destroyed by heat) and 

 brought in contact with the antigen in the presence of complement 

 (supplied by adding fresh guinea-pig serum), the complement will 

 become firmly fixed by the combined antibody and antigen. This 

 fixation of the complement is more thoroughly established when the 

 mixture is placed in an incubator for one hour. If to this mixture, 

 red blood-corpuscles of a sheep and rabbit serum, containing hsemo- 

 lytic amboceptors, are added, no heemolysis will occur because the 

 complement that was added was previously fixed to the antigen by 

 means of the glanders antibodies. 



The serum of a glanders-free horse does not contain antibodies, 

 so if it is mixed with antigen and complement, the latter does not 

 become fixed, but remains free; therefore, when the red blood- 

 corpuscles and the rabbit serum, containing hremolytic amboceptors, 

 are added to such a mixture, hemolysis occurs. 



Positive Reaction. Negative Reaction. 



Antigen + serum-containing antibody Antigen -f normal s e r u m -F comple- 



+ complement + haemolytio ambo- m e n t -f hsemolytie amboceptor + 



ceptor + sheep red blood-corpuaclea sheep red blood-corpuscles =: hsemol- 



= no haemolysis. ysis. 



The complement unites with the anti- There is no antibody to unite the 



gen, through the antibody, hence complement and antigen, hence the 



there is no complement to act complement is free to act through 



through the haemolytio amboceptor the hsemolytie amboceptor on the 



on the sheep corpuscles. sheep red blood-corpuscles. 



This is not a practicable test for the regular practitioner because 

 it requires special laboratory apparatus and very accurate technie. 



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