480 APPLICATION Of METHODS OF BACTERIOLOGY 



An antitoxic serum of this strength, therefore, contains 

 10 times the normal amount of antitoxin, because it con- 

 tains the immunity unit in only 0.1 c.c.; a normal anti- 

 toxin being one in which an immunity unit is contained in 

 one cubic centimeter. Antitoxic serums are frequently of 

 such high degree of potency that they contain from 800 

 to 1000 immunity units in each cubic centimeter. 



