2 Prof. E. Muir and Mr, C. H. Browning. [May 17, 



A particular anti-complement has, as a rule, the greatest neutralising 

 effect on the complement used for its production, though it may have 

 an action also on the complements of some other animals, whilst on 

 others still it has little or no effect. This would point to a difference 

 in the haptophore groups of the several complements. Yet these may 

 be effective in haemolysis, i.e., they may combine with the E + IB 

 molecules, and therefore the haptophore groups of these different 

 complements would appear to be the same. This apparent contra- 

 diction has been discussed by Bordet* and by Ehrlich and Morgenroth,f 

 and the latter observers suggest that there may be more than one 

 immune-body, one combining with the complement of animal A and 

 another combining that of animal B. It seemed to us that this and 

 other questions might be investigated by the method devised by one of 

 us,J by means of which the amount of complement taken up by the 

 E+IB molecules can be estimated. We can thus determine whether 

 these molecules saturated for the complement of one species are also 

 saturated for that of another species. The present paper falls into two 

 chief parts, the first dealing with the combining affinities of complement 

 for anti-complement and for E + IB molecules respectively, the second 

 dealing with complementoids. 



The methods used of estimating the value of immune-body and of 

 complement are those of Ehrlich arid Y. Dungern, as explained in a 

 previous paper. We shall use the following abbreviations : C = 

 complement, anti-C = anti-complement, IB = immune body, E = the 

 receptors of the red corpuscles which combine with immune-body. 

 M.H.D. = minimum haemolytic dose. When we are speaking of 

 doses, a numeral is placed before the symbol, thus, SIB will mean three 

 times the amount of immune-body necessary for haemolysis in presence 

 of excess of complement, and 3E + 3IB will signify three doses of IB, 

 combined with the corresponding number of receptor's of the red cor- 

 puscles; E + IB + C will, of course, indicate a condition leading to com- 

 plete haemolysis. 



I. On the Combining (Haptophore) Group of Complement. 



(a) On the Firmness of the Combinations of Complement. In the first 



J may consider the relative stability of the combination 



h E + IB on the one hand and the combination C + anti-C on the other 



t has been shown by one of us in a previous communication that 



iicular instance studied there is no evidence that C after 



1 Bordet, ' Annales de 1'Inst. Pasteur,' 1901, p. 303. 



Ehrlich and Morgenroth, op. cit. 

 I Muir, ' The Lancet,' 1903, vol. 2 t> 



P TA . i J XT " 



