BACTERICIDAL OR ANTI-BACTERIAL IMMUNITY. 183 



haemoglobin from the stromata, with a partial destruction of the latter. l 

 Now Bordet injected a few cubic centimetres of the whipped blood of 

 the rabbit, containing the serum and red blood cells, into the subcutane- 

 ous tissue or peritoneal cavity of normal guinea-pigs. This operation, 

 which does not markedly interfere with the well-being of guinea-pigs, 

 was repeated five or six times with intervals of a few days. When now 

 blood was drawn from the treated pig, allowed to clot, and the clear 

 serum secured, it was found to have become markedly lytic for rabbit 

 corpuscles. A very small proportion, mixed with rabbit's blood diluted 

 with physiological salt solution, in a short time brought the haemoglobin 

 into a clear ruby solution in which the stromata or "ghosts" of the cor- 

 puscles floated as a pale and scarcely visible cloud. This process is called 

 haemolysis : serum possessing this capacity is called hcemolytic or hcemotoxic 

 serum. 



This adaptation of one animal to the red blood cells of another species 

 may be accomplished without difficulty with a great variety of animals. 



But a most remarkable thing about this newly acquired lytic capacity 

 of the serum is that it is limited to the red corpuscles of the species of 

 animal whose blood was used for the injection in Bordet's experiment 

 to the corpuscles of the rabbit. Eed blood cells of the dog, cat, sheep, 

 bovines, fowl, etc., are no more affected by this serum of a guinea-pig 

 which has been adapted to the blood of the rabbit than they were before. 

 In other words, the adaptation to foreign corpuscles is specific. 



The statement that this adaptation to alien blood is specific that is 

 to say, that the serum becomes active only for the corpuscles of the spe- 

 cies injected, should be so qualified as to recognize the curious fact that 

 a slight degree of lysis may often be induced in corpuscles of species of 

 animals very closely related to those from which the injected blood is 

 derived. For example, if a rabbit be adapted to human blood by iutra- 

 peritoueal injections, the serum of this rabbit, now strongly lytic for the 

 corpuscles of man, may be slightly lytic for the corpuscles of monkeys. 

 Similarly, serum artificially lytic for the red cells of goats may be slightly 

 lytic for those of sheep, but not for the corpuscles of cats, dogs, man, etc. 



This form of test, delicate beyond anything hitherto known in physi- 

 ological chemistry, may thus prove of value in defining the relationships 

 and limitations of animal species. 



This preliminary observation of Bordet was followed by a series of 

 studies upon artificial haemolysis, the results of which we can only 

 briefly summarize. In the first place, to what is this remarkable acquired 

 lytic capacity of the serum due ? Bordet heated for half an hour to 56 C. 

 some of the lytic serum secured by adapting the guinea-pig through sub- 

 cutaneous injections to the red blood cells of the rabbit. He found that 

 it had completely lost its new lytic power. But when he now added to 



1 While the serum of the guinea-pig i 

 rabbit, the serum of the rabbit is lytic for 

 normal rabbit serum is not lytic for the beef 

 coipuscles of rabbits and guinea-pigs. 



