Pleuro- Pneumonia of Cattle. 209 



with saline, and it should now contain no conglutinin. The ab- 

 sence of conglutinin can be tested for by adding this supernatent 

 fluid to another amount of washed goat cells, and noting whether 

 any conglutination occurs. It has been found that one applica- 

 tion of 10 c.c.s. of a 10 per cent, suspension of goat's cells was 

 sufficient to extract all the conglutinin from 1 cc of any one 

 of the bovine sera, which have been treated in this way. The 

 bovine serum dilution, after the conglutinin has been extracted, 

 is then heated in a water bath at 56°C. for 30 minutes, to destroy 

 any complement which may remain. On submitting this treated 

 bovine serum to a test for complement fixation, it is found that 

 it gives a negative reaction, whereas untreated serum No. 94 

 gives a strongly positive reaction. 



From the results obtained in the experiments outlined above 

 it is obvious that, while it is possible to extract conglutinin from 

 bovine serum, the extraction of conglutinin also brings about the 

 disappearance of the specific antibodies; consequently, sera so 

 treated are useless for the purposes of complement fixation tests 

 for the diagnosis of contagious pleuro-pneumonia. 



Conclusion. 



(1) Agglutinins could not be demonstrated, in the serum 

 taken from bovines known to be affected with contagious pleuro- 

 pneumonia, by the usual macroscopic and microscopic methods of 

 testing for agglutinins. Therefore an agglutination test apparently 

 has no value as a means of differentiating between animals which 

 are, and which are not, affected with the disease. 



(2) Complement fixing antibodies are present in the serum of 

 animals affected with the disease, and a complement fixation test 

 can be used to differentiate infected from non-infected animals. 



(3) In order to obtain reliable results with the complement 

 fixation test, the special technique outlined in the proceeding 

 pages must be closely followed in every particular. 



(4) The main difficulty in carrying out complement fixa- 

 tion for the diagnosis of contagious pleuro-pneumonia is to pre- 

 vent errors arising in the test owing to the presence of con- 

 glutinin in the test serum. 



(5) Bovine serum, from which the conglutinin has been ex- 

 tracted by adopting the methods outlined in the preceding pages, 

 is rendered useless for the purposes of a complement fixation test 

 owing to the inability to prevent, with extraction of the con- 



