Pleuro- Pneumonia of Cattle. 197 



earlier experiments with pure culture as antigen, and with sera 

 obtained from known positive cases of contagious pleuro- 

 pneumonia could be explained. 



In concluding this section on conglutinin it is perhaps worthy 

 of mention that amongst the many experiments carried out with 

 ■conglutinin was an experiment to determine whether a modi- 

 fied conglutination reaction, possessed any diagnostic value in 

 contagious pleuro-pneumonia. For this experiment, culture and 

 a known positive serum were mixed together in graded doses, and 

 .allowed to remain in' the incubator for 12 hours. At the end of 

 that time complement was added to each tube. It was thought 

 that the combination of culture (antigen) and positive serum 

 (antibody) would be conglutinated by the combined action of 

 •conglutinin and complement. 



Although encouraging results were obtained at first, it was 

 soon demonstrated that this method was quite unreliable for 

 •diagnostic purposes. 



Quantitative Relationship between Complement and 

 Amboceptor in the Production of Haemolysis. 



Morgenroth and Sachs (1902) (11) have demonstrated that 

 within certain limits there exists an inverse relationship between 

 haemolytic amboceptor and complement in the production of 

 haemolysis. If for a given quantity of red blood cells a certain 

 quantity of haemolytic amboceptor and complement is required 

 to bring about complete haemolysis, reduction of either the com- 

 plement or amboceptor necessitates an increase of the other fac- 

 tor. 



Noguchi (1911) (14) has shown that in the presence of one 

 unit of haemolytic amboceptor, 0.1 c.c. of guinea-pig's comple- 

 ment is required to produce complete haemolysis of a given quan- 

 tity of red blood cells in a given time, while, by using 4, 8, and 

 20 units of amboceptor, complete haemolysis of a similar quan- 

 tity of red blood cells is obtainable in the same time with 1/3, 

 1/5, and 1/10 of the 0.1 c.c. of complement respectively. 



This inverse relationship between amboceptor and complement 

 is of the utmost importance in complement fixation work in con- 

 tagious pleuro-pneumonia, because it enables us to overcome 

 the action of conglutinin to a certain extent. 



If in the standardisation of the haemolytic system for com- 

 plement fixation in contagious pleuro-pneumonia, the unit of com- 



