PROPERTIES OF ANTISENSITIZERS. 289 



just discussed, it would seem superfluous to add that if normal 

 rabbit serum, 56 degrees, is added in the first place to the anti- 

 serum the latter loses its power to protect sensitive corpuscles 

 from alexin. It is indeed obvious, since even when the corpuscles 

 have been cured by antiserum the subsequent addition of normal 

 rabbit serum will neutralize the protection already afforded. 



Another fact resulting from the evidence of the preceding experi- 

 ment is that sensitized ox corpuscles cured with antiserum and 

 washed, and resistant to guinea-pig or human alexin, will be hemo- 

 lyzed by rabbit alexin, since this serum restores the sensitization. 



Is the power of annulling the cure of corpuscles by antiserum 

 present in normal rabbit serum that has been heated to tempera- 

 tures considerably above 56 degrees? Heating to 70 degrees for a 

 half hour will not destroy it. On the other hand, the fluid ex- 

 pressed from a clot of serum coagulated at 100 degrees no longer 

 retains this power. The power is only feebly, if at all, present in 

 rabbit aqueous humor heated to 56 degrees. It is evident, then, 

 that if it be due to normal sensitizers, as is likely, they are not 

 present in the aqueous humor. This fact is in harmony with our 

 experimental results published in 1895, in which we demonstrated 

 that the bactericidal power of cholera serum is due to the collabora- 

 tion of two distinct substances, one a specific one which is ther- 

 mostable and occurs only in the serum of vaccinated animals 

 (preventive substance or sensitizer) ; and the other, the alexin, or 

 proper bactericidal substance, destroyed at 55 degrees, and present 

 in the serum of both normal and vaccinated animals in approxi- 

 mately equal amounts. The familiar experiment of mixing the 

 aqueous humor (56 degrees) of an immunized animal with fresh 

 serum of a normal animal and vibrios gave no bacteriolysis; bac- 

 teriolysis was energetic, however, if heated serum from the same 

 animal replaced the aqueous humor. In other words, aqueous 

 humor contains no sensitizer. 



(F) If we find that a given antiserum neutralizes, as does the 

 one we are studying, several different specific sensitizers, each 

 active against different cells, but all derived by immunizing animals 

 of the same species, are we to conclude that this antiserum contains 

 several different antiscnsitizers, each one of which combines with 

 a separate sensitizer? Or are we to conclude that the antiserum 



