1904.] Combining Properties of Serum- Complements, etc. 17 



thus seen that a mere fraction of Cd entered into combination with 

 the R + IB molecules before lysis. We may add that the largest 

 amount observed was in an experiment with rabbit's Cd, where it 

 came out that of 0*25 c.c. of Cd added before lysis an amount was 

 taken up equal to O'l c.c. of Cd added after lysis. 



From all these experiments it is shown that before lysis Cd has a 

 weak affinity for E, + IB molecules, and that in any given case only 

 a fraction of the amount added enters into combination. This result 

 is of high importance in connection with the general question as to 

 the action of these substances, since it implies that the action of one 

 substance complement increases the combining affinity of another 

 substance complementoid. 



On the Saturation of the R + IB Molecules with Complementoids, after 



lias occurred. 



Seeing that red corpuscles treated with multiple hsemolytic doses of 

 IB take up multiple doses of C, we may produce lysis by a single dose 

 of C, and then find whether the affinities of the remaining R + IB 

 molecules can be satisfied with Cd. The different stages of such 

 experiments are (a) The addition of several doses of IB to the 

 corpuscles, time being allowed for combination ; (b) Lysis by a single 

 dose of C; (e) The addition of Cd in excess; 2 hours at 37 C. are 

 allowed for combination ; (d) The addition of about one dose of C ; 

 1 hour at 37 C. for combination ; (e) The addition of red corpuscles 

 treated with IB to test for the presence of free C. (In case the 

 haemolytic value of C should fall during the experiment, the same 

 amount of C as that used in (d) should be added to a little salt solution 

 and placed in the incubator at the same time for an hour ; its value is 

 then tested by adding red corpuscles treated with IB.) We can in 

 this way test the saturating power of rabbit's or guinea-pig's Cd with 

 rabbit's or guinea-pig's C four possible combinations. A considerable 

 number of experiments of this kind have been carried out, but the 

 general result may be stated that after saturation with Cd not more 

 than a fraction of a dose of the added C has been taken up. 



Examples 1 and 2. Saturation with Rabbit's Cd. 

 Test with Rabbit's and Guinea-pig's C. 



M.H.D. of IB = 0-002 c.c. 



guinea-pig's C = 0'045 c.c. 



rabbit's C = 0'll c.c. 



(0*5 c.c. of suspension of red corpuscles is used, so that the doses will 

 be half the amount.) 



5D of IB added to 4 tubes, A, B, C, D. 



VOL. LXXIV. C 



