74 PROPERTIES OF H^EMOLYTIC SERA 



/. Immune-body to Guinea-pig's Corpuscles (obtained by 

 injecting the Rabbit with these corpuscles). 



(a) With Guinea-pig's Complement 



We may first compare the results when guinea-pig's 

 complement is used with those when rabbit's complement 

 is used. In the former case the dose of complement is very 

 high ; in fact, more than ten times the amount of guinea- 

 pig's complement sufficient to haemolyse ox's corpuscles is 

 necessary to haemolyse its own corpuscles. This might be 

 due to the fact that only a fraction of the complement 

 molecules suited the immune-body to guinea-pig's corpuscles, 

 or it might be due merely to weakness of the toxic action 

 of the complement. If the former were the case, the 

 presence of the uncombined complement would be shown 

 by adding the corpuscles of another animal treated with 

 the corresponding immune-body. The matter is put to 

 the test by adding varying amounts of guinea-pig's com- 

 plement to guinea-pig's corpuscles with their corresponding 

 immune-body, and then after allowing two hours at 37 (X 

 for combination, to test for the presence of complement by 

 means of ox's corpuscles treated with their immune-body. 

 If we use 1 D of immune-body to indicate the amount 

 necessary to produce lysis when rabbit's complement is 

 used, then 10 D will be the M.H.D. when guinea-pig's com- 

 plement is used. The following are the chief results which 

 we have obtained. It is to be noted that, of course, if less 

 than 10 D of IB is added complete lysis does not occur with 

 guinea-pig's complement, and in such cases the tubes are 

 centrifugalized and the clear fluid is added to the indicator, 

 i.e. ox's corpuscles treated with their immune-body. This 

 indicator is specially suitable on account of the high sensi- 

 tiveness of the corpuscles to guinea-pig's complement. 



Such an experiment may be graphically represented thus 



Guinea-pig's O + n IB + x guinea-pig's C j + Ox's O + IB 



