THE SENSITIZERS OF SERA. 249 



(6) Same as last tube, with heated normal rabbit serum replacing 

 the specific serum. 



These mixtures are left, as usual, for 5 hours at room tempera- 

 ture and then one-thirtieth of a cubic centimeter of sensitized hen 

 corpuscles is added to each tube. 



The results are wholly in harmony with those already de- 

 tailed. The corpuscles are destroyed by the alexin in "6"; in 

 "a ;; , on the contrary, there is no hemolysis. The rabbit serum 

 specific for dog blood has fixed the alexin when dog serum is 

 present; in addition to Tchistovitch's precipitin there is also a 

 sensitizer, as in the case of rabbit > milk serum and rabbit > 

 egg serum. 



The serum of guinea-pigs treated with heated rabbit serum. We 

 decided to study this combination on account of certain peculi- 

 arities that it was known to present. We know from Bordet's 

 researches that, contrary to the general rule, guinea-pigs injected 

 with rabbit serum form no precipitin for this serum. On account of 

 this unusual occurrence the question might well arise as to whether 

 multiple injections instead of the usual two injections might not 

 give a different result. We therefore gave our guinea-pigs six 

 successive injections of from 4 to 5 c.c. of rabbit serum. By this 

 means we obtained a serum which, although it produced no real 

 precipitate, did give rise to a distinct opalescence when rabbit 

 serum was added. 



As we presupposed from the work of others, the guinea-pig pro- 

 duces only very weak precipitins to rabbit serum. We have also 

 tested for the presence of a sensitizer in this "guinea-pig > rab- 

 bit" serum. We found that guinea-pig alexin is indeed fixed by a 

 mixture of rabbit serum and heated guinea-pig > rabbit serum; 

 this fixation, however, is distinctly less than in the other instances 

 considered and is indeed a mere delay in hemolysis rather than a 

 total inhibition. We consider, however, that a sensitizing property 

 may be claimed for this serum, although it is as slight as is the 

 precipitating property. 



The serum of rabbits treated with pure horse fibrinogen. We 

 wished to determine whether injecting pure fibrinogen into rabbits 

 would lead to the formation of sensitizers for this chemically pure 

 substance, as we already know that coagulins for the globulins, 



