308 Prof. R Muir and Mr. C. H. Browning. [Nov. 10, 



It is to be noted that almost all the R -f IB molecules capable of taking 

 up complement are present after the addition of one dose of immune- 

 body, and that the subsequent addition of the same immune-body molecules 

 scarcely increases the amount of complement taken up, though these 

 molecules combine with the receptors of the red corpuscles. It would 

 therefore appear that the failure on the part of an R + IB molecule to 

 combine with complement, is due in some way to the receptors and not 

 to the immune-body. According to Ehrlieh's theory the amboceptor 

 (immune-body) has practically no affinity for complement in the free 

 state, but acquires that affinity when combined with the tissue or 

 bacterial molecule. But the result above stated would, according to 

 the amboceptor hypothesis, imply that only some molecules capable 

 of combining with immune-body give the latter affinity for comple- 

 ment. According to the view that the immune-body renders the tissue 

 molecule capable of taking up complement, the explanation would 

 simply be that some of the molecules of the ox's corpuscles have no 

 combining-group for the ox's complement, though they enter into 

 combination with immune-body. It is not possible on theoretical 

 grounds to establish either of these hypotheses by the exclusion of the 

 other, but whichever may be ultimately established, the importance of 

 the nature of the tissue molecule in determining whether complement 

 will be taken up or not is brought out with sufficient clearness. 



If we consider the action of guinea-pig's and rabbit's complements, 

 it will appear that the striking variations in dosage brought out in the 

 original tables, are due to the zymotoxic and not to the haptophore 

 group. The combining relationships of the two complements may be 

 compared in another way, viz., by adding a large amount of immune- 

 body, say ten doses, and finding the ratio of rabbit's to guinea-pig's 

 complement taken up in the case of the three sera. We have carried 

 this out, and the following are the results. It was found most 

 convenient to compare only two sera on the same day. Manifestly, 

 only the two ratios in the same experiment are comparable. 



Experiment LXX of two Cs. 



Ox's corpuscles 10 D IB took up 0'44 c.c. guinea-pig's C "I , -^ 



0-56 rabbit's C J 



Guinea-pig's corpuscles. . 0'48 guinea-pig's 01, ,,* 



0-56 rabbit's C J 

 Experiment LXXI 



Ox's corpuscles 10 D IB took up 0'18 c.c. guinea-pig's C 1 , 



0-48 rabbit's C J 



Guinea-pig's corpuscles . . 0'28 guinea-pig's 01, 



0-6 rabbit's C J 

 Experiment LXXII 



Ox's corpuscles 10 D IB took up 0'26 c.c. guinea-pig's 01, 



0-36 rabbit's C J 



Babbit's corpuscles '36 guinea-pig's C 



0-54 rabbit's C 



