BACTERICIDAL SERUMS. 253 



to kill all the organisms which have been intro- 

 duced, and yet the animal may die with the intoxi- 

 tion of cholera. Furthermore, if one. considers a 

 culture of the cholera vibrio, which has been killed 

 by heat, as representing so much cholera toxin, 

 anticholera serum protects against no more of it 

 than does the same quantity of normal serum. It 

 is believed that anticholera and similar immune 

 serums may even increase intoxication by dissolv- 

 ing the bacteria and thus liberating an excess of 

 endotoxin. 



We have little positive knowledge concerning the origin of 

 organs which form the bactericidal substances in substances" 

 acquired immunity. Pfeiffer and Marx, in rela- 

 tion to cholera, and Wassermann in typhoid, found 

 that the spleen and the hemopoietic organs in gen- 

 eral contain the immune bodies in greater concen- 

 tration than the blood serum, and in immunization 

 experiments the bodies may be demonstrated in 

 these organs at a time when they are absent from 

 the circulation. This fact is generally accepted as 

 proof of their formation at these points. Wasser- 

 mann and others have demonstrated the presence 

 of complement in the leucocytes, and Metchnikoff 

 holds that it is produced only by such cells. (See 

 origin of agglutinins, Chapter XIII.) 



The standardization of bactericidal serums is at standard- 

 present more of theoretical than of practical in- 

 terest, because of their limited therapeutic use. 

 Their values can not be determined with the ac- 

 curacy with which one measures a unit of anti- 

 toxin. One may deliver from a pipette a definite 

 quantity of toxin and if the toxin has been well 

 preserved the same quantity may be obtained at 



