]38 JOHNE^S DISEASE 



can hardly be performed to give any degree of 

 accuracy except by those habitually carrying it out. 



The technique to be followed is similar to that used 

 in performing the reaction with a suspected tuber- 

 cular serum. Special care should be taken to titrate 

 accurately the complement before each series of bloods 

 is tested. At the Brown Institution a simple emulsion 

 of bacilli was used as antigen, but it is possible that 

 a better antigen would be obtained if an extract made 

 from diseased bowel were added to the bacillary emul- 

 sion, as recommended by Hammer for tuberculosis. 

 On the other hand, it is worthy of note that Miessner 

 and Kohlstock were unable to obtain any satisfactory 

 results when they used as antigen an antiformin 

 extract, etc., of diseased gut which they called 

 " enteritidin." 



The tests which are detailed below were carried 

 out on seven naturally infected bovines at the Brown 

 Institution, the animals being the same as those used 

 for the agglutination tests (Nos. i to 6; see table, 

 p. 126). Of these animals, Nos. i, 4, 5, 6, and 7 gave 

 positive reactions. No. 3 a doubtful reaction, and No. 2 

 a negative. A few of the animals were tested several 

 times, and on every occasion gave the reaction with 

 more or less the same intensity. It may be mentioned 

 here that in most of the animals the disease was in 

 an advanced stage. In five experimentally inoculated 

 calves (Nos. la, 2a, 3^, 4^, 5«, Chapters VII. and IX.), 

 mentioned also under the agglutination tests, which 

 had received an emulsion of Johne's bacillus six 

 months previously, the reactions were negative, except 

 with No. s^t which gave a slight positive result. 

 At the time the blood was taken, these animals were 

 really in the incubation period of the disease, as they 

 showed no diarrhoea or any other symptoms ; but, on 



