1910.] Recognition of the Individual by Hcemolytic Methods. 419 



same times, gave quite different isolysiiis. In fact the isolysins formed depend 

 upon two distinct factors : — 



(a) The individuality of the injected corpuscles. 



(b) The individuality of the animal into which they are injected. 



"When we consider the enormous number of variations possible in each of 

 these factors, we see the almost unlimited possibilities in the resulting 

 sera. 



In view of the aliove it should be possible by taking a mixture of a 

 sufficiently large number of immune sera and exhausting this with the 

 corpuscles of one individual, to obtain a serum which is specific for the 

 corpuscles of this one individual ; i.e. which has no hcemolytic action on these 

 corpuscles, but ha?molyses those of all other individuals of the same species. 

 To test this, a mixture was made of the sera of between 60 and 70 immune 

 Egyptian cattle. This mixture was then exhausted with the corpuscles of a 

 normal Cyprus bull and then tested on the washed corpuscles of 20 immune 

 Egyptian cattle, two normal Cyprus cattle, and the above mentioned Cyprus 

 bull with whose corpuscles the mixture had been exhausted. For the test 

 equal parts were taken of — 



(a) The exhausted serum ; 



(b) A 5 per cent, suspension of the washed red blood corpuscles ; 



(c) A one-tenth dilution of fresh guinea-pig serum in normal saline. 



The tubes were kept at 37° C. for one hour and then left over-night in the 

 ice-safe ; after which the results were read off. 



It was then found that complete hsemolysis had occurred in all the tubes, 

 with the exception of the control tube containing corpuscles of the Cyprus 

 bull with which the serum was exhausted. The " exhausted " serum was thus 

 able to pick out, quite sharply, the corpuscles of one individual from those of 

 22 others. Following up these results, a second and more extensive test was 

 made. In this case the same immune serum was used ; it was, however, 

 exhausted with the corpuscles of another normal bull. 



This exhausted serum was then tested on the corpuscles of 110 different 

 cattle (3 Soudan, 34 Cyprus and 73 Egyptian). 



In this test again all the tubes showed complete htemolysis with the 

 exception of the one containing the corpuscles for which the serum had been 

 " exhausted." This control tube showed no trace of hsemolysis. 



A number of other tests have been made by exhausting the serum with the 

 corpuscles of various individuals, and the general rule has so far always held 

 except in one case. The serum exhausted with the corpuscles of a cow was 



