EXPERIMENT STATION BULLETINS. ' 271 



the infectious stage is past. These tests merely show then, that com- 

 plement fixing and agglutination antibodies are present in the blood 

 of such animals and since the tests mentioned are specific for Bad. 

 ahm'tus infection, it is certain that reacting animals are or have at 

 some time been infected with this particular organism. 



It has been suggested that before buying an animal it should be 

 tested with one or both of these tests, and if the animal reacts one 

 should not buy it. If that cow were immune and did not harbor the 

 Bad. abortus in her body, would it not be safe to introduce her into 

 any herd? Then again the cow might show negative tests and still 

 abort after being placed into a new herd. Immunization with Bad. 

 abwtus vaccines and bacterines is being encouraged but is not yet 

 fully accepted as a reliable means of prevention, and there is no test 

 which will estimate the degree of immunity in the vaccinated animal. 



It is difficult to accurately measure the value of immunizing agents 

 in infectious abortion for a number of reasons. Kesults are very 

 apt to be post hoc non propter hoc due to the development of a 

 natural resistance with age or to an acquired immunity from previous 

 invasions or infections by Bact. ahori'us. Furthermore, it is quite im- 

 proper to estimate results wholly on the basis of fetuses lost or de- 

 livered prior to full term since the loss of the fetus is only one of the 

 serious manifestations of abortion disease of cattle. 



If some test could be perfected through which a distinction might 

 be made between infected and immune animals it would greatly facili- 

 tate future research on infectious abortion. The work of Fleischner 

 and Meyer (2) indicates that such a thing may be possible. These 

 investigators found that guinea pigs infected with Ba\d. abortus gave 

 a definite and specific reaction to the intradermal "abortin" test, while 

 guinea pigs treated with a suspension of dead abortion bacilli failed to 

 react. Both infected and injected (with dead organisms) pigs reacted 

 to the complement fixation aud agglutination tests. The intradermal 

 "abortin" test had previously been employed by Reichel and Harkins 

 (3) in cattle. After having examined three herds, a total of seventy 

 animals, in which thirty-nine abortions had occurred they found that 

 all animals reacted to either the complement fixation test or the ag- 

 glutination test or both and twenty animals reacted to the intrader- 

 mal "abortin" test. Five animals that reacted to the "abortin" test 

 had not aborted but were from herds where abortion disease was prev- 

 alent. Herd No. B. consisting of five animals showed a normal his- 

 tory with no abortions, all animals showed reaction to one or both 

 serum tests but none reacted to the intradermal test. In view of their 

 results they concluded that, "With much to be desired in the applica- 

 tion and interpretation of all the tests or means at hand to establish 

 a diagnosis, the intradermal abortion test deserves recognition in that 

 it can be applied by the veterinarian without assistance." 



Experiments on the intradermal test were started by the writer in 

 the early part of the summer of 1919 and the following data represent 

 the results thus far obtained. 



