CHAPTER VIII 



THE AGGLUTINATION REACTION AND THE 

 COMPLEMENT FIXATION TEST 



The Agg-Iutination Test. — The presence of agglu- 

 tinins in the serum of bovines suffering from Johne's 

 disease can be demonstrated in the ordinary way 

 (C. C. Twort); but, as in the case of tuberculosis, 

 a positive reaction cannot be obtained with a highly 

 diluted serum. Animals experimentally inoculated 

 also produce agglutinins ; not only bovines which 

 subsequently contract the disease, but also such 

 animals as rabbits and fowls, to which, up to the 

 present time, the disease has never been transmitted. 

 Needless to say, the sera of experimental animals 

 should always be tested before the first injection is 

 made, as the normal serum may possibly agglutinate. 

 Although we have not found any normal rabbits give 

 positive reactions, we have had to discard one or two 

 fowls on this account. In considering the dilutions of 

 the sera, they refer in all cases to a complete reaction, 

 a partial agglutination often being obtained with a 

 much higher dilution. 



Technique. — This is extremely simple, and the same 

 as that used for testing a suspected tubercular serum, 

 with the following difference : 



To obtain the best results in the last-mentioned 

 cases it is usual to employ a homogeneous broth- 



135 



