UNION OF COMPLEMENT 35 



to be used must be completely freed from the natural 

 immune-body for ox's corpuscles, which it possesses in 

 varying amounts. This is of course done by adding 

 washed ox's corpuscles to the serum for an hour at C., 

 and then centrifugalizing.) 



Having thus seen that it is not possible to completely 

 lock up the molecules of immune-body combined with the 

 receptors of the corpuscles by means of excess of comple- 

 ment, we have now to inquire whether the complement 

 really diminishes the amount of immune-body which can 

 be separated. In this case we compare the amount of 

 immune-body which is recoverable, in one instance before 

 the addition of complement, in the other after the saturation 

 with complement. We proceed as follows : Two series 

 (A and B) of nine tubes, each containing 1 c.c. of the standard 

 suspension of red corpuscles, are taken and increasing amounts 

 of immune-body are added to these, say from two doses 

 in the first tube up to ten doses in the ninth tube ; time is 

 allowed for combination of the immune-body, the tubes 

 are centrifugalized and the corpuscles are washed several 

 times in salt solution. All the immune-body is thus in 

 combination. We then proceed further : 



Series A. To each tube is added 1 c.c. of suspension 

 of red blood corpuscles ; the tubes are shaken, and are 

 placed in the incubator for an hour at 37 C. ; to each 

 tube four doses of complement are added, and the tubes 

 are replaced in the incubator for an hour. The result is 

 read on the following morning. (Complete lysis of all the 

 first set of corpuscles of course occurs, and lysis of the second 

 in proportion to the amount of immune-body which has 

 been dissociated.) 



Series B. To each tube is added more complement than 

 can be taken up through the medium of immune-body 

 (this amount can be calculated by means of other experi- 

 ments) ; the tubes are then placed in the incubator for 



D 2 



