306 Prof. R Muir and Mr. G. H. Browning. [Nov. 10, 



hsemolytic dose of rabbit's complement. This phenomenon is, probably, 

 related to the fact brought out by Morgenroth and Sachs,* that the 

 M.H.D. of complement sometimes varies greatly, according to the 

 amount of immune-body used, and, conversely, the M.H.D. of immune- 

 body may vary greatly, according to the amount of complement. The 

 explanation of this is also outside the scope of the present paper. 



(b) With Guinea-Pig's Complement 



The combination of guinea-pig's complement may be exemplified by 

 the following : 



Experiment LXII. 1 D of IB took up 0'04 c.c. guinea-pig's C. 

 10 0-36 



LXIIL 1 D of IB took up 0-012 c.c. guinea-pig's C. 

 10 0-27 



The indicator was ox's corpuscles treated with immune-body. Here 

 we have variations corresponding to those noted above. 



We have also found that with this immune-body a small quantity of 

 guinea-pig's complement keeps out of combination a certain amount of 

 rabbit's complement, and that saturation with rabbit's complement 

 implies practical saturation for guinea-pig's complement also. A 

 similar statement applies to rabbit's complement keeping out guinea- 

 pig's complement. 



(c) With Ox's Complement 



Owing to the lack of serum, we have been unable to study the 

 combining relationships of ox's complement through the medium of this 

 immune-body. This defect, however, cannot modify the main conclu- 

 sions arrived at. 



///. Immune-body to Ox's Corpuscles (obtained by injecting the Rabbit). 



It will be seen from the tables above that the dose of immune-body 

 is practically the same with guinea-pig's as with rabbit's complement. 

 The dose of the latter complement is the higher, and in a previous 

 paperf it was shown that this was probably due to a smaller number 

 of complement molecules in a given volume of serum, rather than to a 

 weaker action of the zymotoxic group. The combining relationships 

 of the two complements have also been fully discussed there, so that it 

 is unnecessary to repeat the results obtained. It is sufficient to say 

 that they behave as regards combination in haemolysis pretty much as 

 if they had the same haptophore groups. We shall refer merely to the 

 action of ox's complement along with the above immune-body. 



With this combination it is usually impossible to produce more than 

 a fraction of lysis in the corpuscles (usually not more than a tenth), no 



* Morgenroth and Sachs, < Berlin, klin. Woch.,' 1902, No. 35. 

 t Muir and Browning, ' Eoy. Soc. Proc.,' June 9, 1904. 



