28 PROPERTIES OF ILEMOLYTIC SERA 



tube there is considerably less than this, and in the last 

 tube considerably more.) The tubes are then placed in the 

 incubator for two hours at 37 C. At the end of this time 

 the combination of complement is practically complete. 

 To each tube is then added a cubic centimetre of sensitized 

 red corpuscles, and the tubes are once more placed in the 

 incubator for an hour and a half and allowed to stand in 

 a cool place till next morning. The results are then read. By 

 this method we can observe (a) the tube in which the added 

 corpuscles have undergone the smallest perceptible degree 

 of lysis, and (b) the tube in which they are completely lysed. 

 The lysis occurring in the added corpuscles might theoretically 

 be due either to free complement or to complement which 

 had become dissociated. As above stated, however, there 

 is no evidence that with the combination used in the experi- 

 ments the latter occurs to any appreciable degree, and 

 accordingly any lysis may be accepted as being due to com- 

 plement which has been left free. In testing whether or 

 not any lysis has occurred in the added corpuscles it will 

 be found a convenient method to pipette off the supernatant 

 fluid, the non-lysed corpuscles having formed a sediment 

 at the bottom of the tube ; to each tube can then be added 

 1 c.c. of distilled water, and the amount of corpuscles can 

 then be tested by the colorimetric method. The fraction 

 of surviving corpuscles subtracted from unity will of course 

 give the amount of lysis which has occurred. 



Of a large number of experiments of this kind performed 

 the following may be cited as examples. The immune- 

 body used in these was obtained from the rabbit by injecting 

 with ox's corpuscles (immune-body, rabbit v. ox). The 

 complement was normal guinea-pig's serum, and was 

 always treated with ox's corpuscles at C. to remove the 

 normal immune-body. For convenience, only six tubes 

 which give the required results are quoted, though as a rule 

 more were used. 



