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



complement and the production of lysis. This may be due either (a) 

 to complementoid failing to combine with the E + IB molecules, or 

 ()~to its being displaced by complement after it has combined ; both 

 factors may be partly concerned. There are two methods by which 

 the question may be investigated, and we have carried out both of 

 them. 



In the first place we may add a given amount of heated serum (Cd) 

 to red corpuscles treated with IB, allow time for combination, then 

 remove the fluid by centrifugalisation, and then test the amount of 

 Cd present in the fluid by finding how much C it will prevent from 

 combining with R + IB molecules after lysis. We shall call the Cd 

 treated in this way Cdx. A control is made with the same amount of 

 heated serum (Cd) which has not been in contact with red corpuscles 

 treated with IB. We have performed a number of experiments of 

 this kind, and the result has always been to show that only a fraction 

 of the Cd combines with the E + IB molecules. In one experiment it 

 was found that the Cdx of the rabbit kept out two-thirds of the 

 amount of guinea-pig's C kept out by rabbit's Cd, i.e., only one-third 

 of the Cd molecules had combined with the intact red corpuscles 

 treated with IB. With guinea-pig's Cdx, in one case a similar result 

 was obtained, whilst in another a half of the Cd molecules had been 

 removed by combination. 



Another method is to bring Cd into contact for a given time with 

 red corpuscles treated with IB (say, SIB), then to centrifugalise and 

 wash these corpuscles, and then test how much C they will take up. 

 The control will be red corpuscles treated with the same amount of 

 IB, but not with Cd. Similar results emerge from experiments of this 

 kind. The following may be taken as an example : 



Three sets of tubes containing the standard amount of red corpuscles, 

 fully 3D of IB added to each tube. 



1. Series A We estimate how much guinea-pig's C will be 

 taken up. 



2. Series B. We estimate how much C will be taken up after the 

 addition of O04 c.c. Cd (lysis having been first produced). 



3. Scries C. The corpuscles are treated with 0-6 c.c. Cd for an hour 

 at 37 C., then centrifugalised and washed to remove the free Cd. 

 We then estimate how much C the corpuscles will take up. 



The result is that in 



Series A 0-175 c.c. of C is taken up. 



* 0-15 



C 0-165 



In other words, after lysis the addition of 0'04 c.c. of Cd has kept 

 out 0-025 c.c. of C, whereas before lysis the addition of 0-6 c.c. of Cd 

 (fifteen -times the amount) has only kept out 0-015 c.c. of C. It is 





