194 



Complement Fixation. 



Bieling & Weichbrodt's observation that the Pfeiffer's 

 bacillus strains they had investigated in complement fixation 

 tests with horse serum, agreed with one another, naturally 

 raises the question whether it might be possible with the help 

 of complement fixation to collect Pfeiffer's bacilli serologically 

 under one heading. 



From the extremely well-marked agglutination differences 

 this must be considered improbable. I have nevertheless carried 

 out a number of complement fixation tests, not with horse 

 serum it as true, but with the same rabbit sera as were used 

 in the agglutination tests. Many of the tests failed on account 

 of inhibition on. the part of the sera or suspensions. A couple 

 of series of experiments however gave reliable reactions and 

 will be reported, as they are very instructive. 



Fresh cultures suspended in salt solution were used in a con- 

 centration which a preliminary experiment had shown did not cause 

 appreciable inhibition in the amount used in the experiment. In 

 each reaction, serum (inactivated for half an hour at 56°), culture, 

 and complement in a total volume of 0.3c.c. were mixed in a series 

 of tubes. The serum was employed in falling quantities: 0.02, 0.01, 

 0.005 c.c. etc. The culture and complement were constant in amount, 

 in the case of the later, H/2 times the minimum haemolytic dose. 

 After remaining 3 / 4 hour at room temperature and 3 / 4 hour at 37° 

 0.2 c.c. of a 2y 2 o/o suspension of sheep corpuscles sensitised with 

 2V2 amboceptor units, was added. The results were read after the 

 tubes had been kept for 1—2 hours at 37°. The figures recorded 

 represent the degree of haemolysis. 



On 7. IV. 21 strain „I 6" was tested against the following sera: 



