260 BIOLOGY OF SPECIALIZED GROUPS 



hyperplasia of chemical side chains, just as we have a hyper- 

 plasia of tissue cells in chronic inflammations. When a certain 

 number of cells have been stimulated by the toxin, the chem- 

 ical side chains from the other cells begin to be secreted into 

 the blood, lymph, and body fluids. These secreted side 

 chains constitute the antitoxin molecules. 



The exact chemical nature of the antitoxin molecule is not 

 known. This is also true of the toxin molecule. It has been 

 shown that the antitoxin of diphtheria is closely associated 

 with the serum-globulin, but this is not prima facie evidence 

 of the antitoxin being a globulin. The antitoxin molecule is 

 evidently of very large dimensions. Most antitoxic molecules 

 do not pass through a porcelain filter of the smallest caliber. 

 The molecules behave like colloids, being electro-negative 

 and therefore move toward the anode of the electrical field. 

 The antitoxin molecules are larger than the corresponding 

 toxin molecules. In their reactions, antitoxins resemble the 

 known protein substances more closely than toxins. They are 

 not as labile as the toxin, but may be altered and destroyed 

 with comparative ease. 



In the commercial preparation of antitoxins healthy horses 

 are immunized to increasing doses of toxin or mixtures of toxin 

 and antitoxin. After a certain period, varying from two to 

 six months, the horses are bled to the extent of five or six liters 

 of blood, and the blood serum which separates out on standing 

 contains the antitoxin (discharged side chains). This anti- 

 toxin is standardized against toxin which has been previously 



