48 PROPERTIES OF H^MOLYTIC SERA 



the R -f IB molecules. It has been shown that a large 

 amount of C can be taken up through the medium of multiple 

 doses of IB, and that the combination of C is a firm one. 

 Thus : 



O 4 I 



2hrs. 



T> r R i Result = no lysis m added 



J-D + 4C i + O | T-D j corpuscles, because all 



the C has been taken up. 



If, however, we add in the same case 3Cd after lysis by 

 1C, but before the addition of the other 30, the result is 

 different, thus : 



2hrs. 



j Result == lysis in 



. T> T> I added corpuscles, 



1 rtt + C i 4- 3Cd ; + 30 1 + O 1 I because some of 

 l * ( L ** \ the C has been kept 



j out by Cd. 



In other words, the Cd molecules have united with the 

 R -f IB molecules after lysis, and have prevented the added 

 C from being taken up ; this is shown by the test corpuscles 

 undergoing lysis by means of the free C. 



To avoid repetition, we may here state that the stages of 

 all such experiments are the following : 



1. To each of a series of tubes containing the standard amount of 

 corpuscles, a certain amount of IB is added, usually three to four 

 hEemolytic doses. 



2. To each tube is added a little more than the hsemolytic dose of 

 complement, and a certain amount of complementoid (heated 

 serum). The tubes are placed in the incubator for an hour at 37 C. 

 Haemolysis, of course, occurs, and time is allowed for the Cd to 

 combine with the II + IB molecules. 



3. To the several tubes in series complement is then added in 

 increasing amount. Experience shows how much C is likely to be 

 taken up, and the last tubes should, of course, contain more than 

 this. The tubes are incubated at 37 C. for two hours. 



