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



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Series A. Guinea-pig's C alone added. Amount taken up = 0'24 c.c. 

 Series B. 0'25 c.c. rabbit's C first, and then guinea-pig's C. Amount of guinea- 

 pig's C taken up = 0'19 c.c. 



Therefore, 0'25 c.c. of rabbit's C has kept from combination about 0'05 c.c. 

 inea-pig's C. 



2. No. 24. M.H.D. of guinea-pig's C = O04 c.c. ; M.H.D. of rabbit's C - 0'3 c.c. 

 About 3D of IB added to each tube as before. 



Series A. Babbit's C alone added ; amount taken iip = 1'35 c.c. 

 Series B. 0'04 c.c. of guinea-pig's first, and then rabbit's C. Amount of 

 rabbit's C taken up = 0'9 c.c. 



Therefore. 0'04 c.c. of guinea-pig's C has kept out 0'45 rabbit's C. 



3. No. 31. M.H.D. of guinea-pig's C = 0'0175 c.c.; M.H.D. of rabbit's C = 

 O'l c.c., 4D of IB added to each tube. 



Series A. Gruinea-pig's C alone added. Amount taken up = O'll c.c. 

 Series 4 B. O'l c.c. of rabbit's C first, and then guinea-pig's C. Amount of 

 guinea-pig's C taken up = 0'09 c.c. 

 Therefore, O'l c.c. rabbit's C has kept out 0'02 c.c. guinea-pig's C. 



Another method is to determine whether R -f IB molecules saturated, 

 , for rabbit's complement are also saturated for guinea-pig's comple- 

 lent. To one series (A) of tubes, each containing the same amount of red 

 corpuscles and the same amount of IB, complement of rabbit is added 

 increasing amounts, and the tubes are placed in the incubator for 

 hours at 37 C. The same procedure is carried out in another 

 jries (B), but at the end of the 2 hours a hsemolytic dose of guinea-pig's 

 is added to each tube. The tubes of both series are placed in the 

 icubator for another hour, and the presence of free C is tested for 

 the usual way. It is evident that the first series will give the 

 )int of saturation with rabbit's C, and the corresponding tube in 

 ic second series will show whether such a tube can still take up 

 linea-pig's complement. As an example, in one experiment it is 

 found that in series A the tube with 0'2 c.c. rabbit's C added gives 

 a fifth of a hsemolytic dose of free C, whilst in series B the tube 

 >ntaining 0*2 c.c. rabbit's C gives a full hsemolytic dose of free C. 

 ?hus it is shown that the tube saturated with rabbit's C took up not 

 more than a fifth of a dose of guinea-pig's C. (A separate estimation 

 carried out at the same time gave O14 c.c. as the amount of guinea- 

 pig's C taken up by the same amount of red corpuscles treated with 

 IB.) It will be shown below that a corresponding result is obtained 

 by saturation with complementoids. 



We have, therefore, shown that in the case studied practically all 

 the molecules of the guinea-pig's complement combine with the same 

 R + IB molecules of the ox as the molecules of the rabbit's comple- 

 ment combine with. 



Another interesting point which presents itself is whether the 

 hsemolytic value of a complement corresponds with the combining 

 value. The haemolytic dose of normal rabbit's serum in the case 



