418 



Dr. C. Todd and Mr. E. G. White. [May 5, 



into the body, it would appear improbable that the organism should, so to 

 speak, go to the trouble of elaborating a haemolytic amboceptor which is 

 practically useless for the only complement with which it is likely to come 

 into contact, and it would seem probable that a suitable complement is really 

 available somewhere in the body although not obviously present to any extent 

 in the serum. 



With a view to seeing if this is really the case, a normal Cyprus bull was 

 injected intravenously with one litre of the mixed serum of ten immune 

 cattle. This serum, although only 24 hours old, showed no action on ox 

 corpuscles "in vitro" if no foreign complement was added; but in the 

 presence of fresh guinea-pig serum was very powerfully heemolytic. (O'Ol c.c. 

 being sufficient to ha^molyse 1 c.c. of 5 per cent, suspension of ox corpuscles.) 

 A few hoixrs after the injection, the urine was very darkly haemoglobin 

 stained, showing that a suitable complement had been forthcoming. 



On testing the serum of the animal a few days later, it was found 

 that, although it had now no hciemolytic action on its own corpuscles, it was 

 distinctly haimolytic for the corpuscles of many other individuals. It was 

 thus possible to " exhaust " the immune serum for one particular corpuscle 

 and to leave it still haemolytic for many others. 



This method of exhaustion " in vivo " was then replaced by exhaustion " in 

 vitro." The technique being as follows : — 



The immune serum was mixed with an equal volume of the washed 

 corpuscles with which it was desired to exhaust the serum ; the mixture kept 

 at 37° C. for an hour, centrifuged, and the serum again treated in the same 

 way with the washed corpuscles and the process repeated a third time. It 

 was then found that the serum had lost all traces of haa^molytic power for the 

 corpuscles in question. 



By means of this method the sera of different immune cattle were 

 now exhausted with the corpuscles of various individuals of the same species 

 and the ha?molytic power of these sera after such treatment was studied on 

 the corpuscles of different individuals. 



It was found that if an immune serum is exhausted with corpuscles 

 of an individual (A), it remains ha;molytic for the corpuscles of many other 

 individuals, but loses its haemolytic power for the corpuscles of some other 

 individuals as well as for those of (A). 



If now a second immune serum is exhausted with the same corpuscles (A), 

 its action on the various corpuscles is not exactly parallel to that of the first 

 serum, and often shows very marked differences. 



This result is to be expected, as it was shown by Ehrlich and Morgenroth, 

 tliat two goats each injected with similar doses of the same goat's blood at the 



