EXPERIMENT STATION BULLETINS. 281 



protection could not be anti-bacterial as the pigs continued to discharge 

 abortion bacilli as evidence by the infection of the males. Further- 

 more the intradermal test indicates the presence of live abortion organ- 

 isms in the body, as it has been shown throughout this work that positive 

 reaction to the intradermal abortin test develops only as a result of in- 

 fection with the abortus bacillus. 



The fact that an animal once has been infected does not mean that 

 it will continue always to react to the intradermal test. This is indi- 

 cated by experiments performed on cattle. Three calves were tested 

 shortly after being born by the serum and intradermal tests. Two were 

 positive to all tests and one was negative. The latter was then infected 

 with Bad. abortus by intravenous injection and developed positive re- 

 actions to a very marked degree to all tests. On repeated testing it was 

 found that all three animals ceased reacting to the intradermal test. 

 The two naturally infected calves reacted to the intradermal test some 

 time after the reaction to the other tests had disappeared. In one case 

 an intradermal reaction was obtained three months after the other tests 

 had become negative. When the animal was tested six weeks later, it 

 was found negative. The artificially infected calf was a male, while the 

 other two were females. The former showed positive complement fixa- 

 tion and agglutination tests after the intradermal test failed to pro- 

 duce a reaction. The complement fixing and agglutinating antibodies 

 were, however, diminishing quite noticeably as evidenced by weaker re- 

 actions. These results support the idea that a permanent infection in 

 calves is improbable. 



Complement fixation and agglutination tests were run on the blood 

 sera and milk of several cows. Bacteriological examinations in the 

 form of guinea pig inoculations were also made of the milk from these 

 cows. The work on the milk was done by Huddleson of this laboratory. 

 Intradermal tests run on these cows compared with the other tests and 

 examinations suggest that this test may be employed as a means of de- 

 tecting the animals which harbor live abortion organisms in their bodies. 

 However, the work in cattle has not progressed sufficiently to warrant 

 any definite conclusions. Work along these lines will be continued by 

 'Mr. Huddleson and it is hoped that the test may be perfected so that the 

 carrier of Bad. abortus can be detected and distinguished from the ani- 

 mals which merely have the abortion antibodies in their serum. 



Keichel and Harkins (3) tested seventy animals and all reacted to 

 either one or both of the complement fixation and agglutination tests 

 while only twenty reacted to the intradermal test. Out of the three 

 herds tested, one herd showed a normal history while in the other two 

 abortions had occurred. In all, thirty-seven animals had aborted, one 

 having aborted three times. Might it not be possible that the thirty-seven 

 animals in those herds were the ones which were actually infected, while 

 the others were immune? If surface presence or tissue invasion, pure 

 and simple, are possible with the Bad. abortus, then it is questionable 

 whether the intradermal test would detect such a condition. Would the 

 agglutination and complement fixation test detect? On the other hand, 

 it seems within reason to believe that an infection may be detected by 

 this test in cattle as well as in guinea pigs. 



