188 G. G. Heslop: 



Serum No. 30 from Experimental Calf 1 (the animal whose 

 serum had previously given a positive agglutination reaction when 

 tested by the macroscopic method) was tested with various cul- 

 ture preparations including Antigen J. There was no fixation 

 of complement in any combination tested, and the haemolysis 

 was just as complete in the positive serum series as it was in 

 the negative serum series put up at the same time. 



Culture preparations (antigens) obtained by the cultivation 

 of virulent serosity from the lungs of the animal supplying posi- 

 tive Serum No. 28, were tested with this latter serum for com- 

 plement fixation. It was found that, in each instance, the re- 

 actions were negative. 



Various other tests were carried out with culture preparations 

 which it is unnecessary to enumerate. Suffice it to say that in 

 no case, using culture as an antigen, was a positive complement 

 fixation result obtained. 



Discussion. 



At this stage it was decided to review that portion of the work 

 relating to complement fixation, in an endeavour to ascertain the 

 reason why, in the tests carried out, it had been impossible to 

 obtain complement fixation with a known positive serum. 



It is conceivable, of course, that filterable viruses in general 

 do not behave in the same way as bacteria, i.e., they may not 

 react to the usual serological tests that bacteria react to. This 

 idea is strengthened by the fact that, although the usual serologi- 

 cal reactions have been tested with a number of other filterable 

 viruses, as well as with contagious pleuro-pneumonia by several 

 experienced workers, the results obtained have either been nega- 

 tive, or else so contradictory that it has been impossible to elab- 

 orate a test, using the ordinary technique of such serological 

 reactions, which could be used with certainty for diagnostic pur- 

 poses. On the other hand it is possible that certain serological 

 reactions can be obtained, provided a special technique is em- 

 ployed, either in the preparation of the component parts of the 

 lest, or in the method of conducting the test, or both. 



Antigens. 



The first question which presented itself on reviewing the 

 -earlier complement fixation experiments was : Were the anti- 

 gens used in those experiments strong enough in a specific sense 

 to bring about complement fixation? It will have been noted 



