446 BACTERIOLOGICAL CHEMISTRY 



Ehrlicli's phenomenon, that L,,. — L^^nMLD, is 

 readily explained, according to Arrhenius and Madsen, 

 as being due to the fact that sufficient toxin must be 

 added to the toxin-antitoxin mixture to overcome the 

 dissociation. This mechanism, however, does not afford 

 a simple explanation of the Danysz phenomenon, although 

 they quote a chemical reaction somewhat, though not 

 completely, analogous. If sodium hydroxide is added to 

 monochloracetic acid the sodium salt is formed : — 



4CH2CI.COOH + 4NaOH > 4CH2Cl.COONa + 4H2O. 



If half the sodium hydroxide is added at 70° C, however, 

 a second reaction takes place, the chlorine atom being 

 split off with formation of glycollic acid : — 



700 C. 

 4CH2CI.COOH +2NaOH > CHaOH.COONa +NaCl + H2O +3CH2CI.COOH. 



On adding the remaining half of the sodium hydroxide 

 at the normal temperature, one molecule of monochlor- 

 acetic acid will remain unneutralised (corresponding to 

 an excess of toxin, as in the Danysz phenomenon). 



This mechanism does not account, either, for the dilu- 

 tion effects observed in toxin-antitoxin reactions. If 

 equivalent quantities of toxin and antitoxin are mixed 

 in strong solution to give a non-toxic mixture, the solution 

 remains neutral on dilution. If, however, the reagents 

 are diluted before mixing the neutralisation is not com- 

 plete, although if the Law of Mass Action applied, the 

 result should be the same in each case. 



Bordet regarded the toxin-antitoxin reactions as 

 following the ordinary course of colloidal adsorption 

 reactions, where the amount of adsorption depends on 

 the relative concentration of the reagents. Thus ac- 

 cording to Freundlich's adsorption isotherm, x=maC'^, 

 where a;=the amount adsorbed, (7= the concentration of 

 the remaining unadsorbed substance, m=the amount of 

 adsorbant, and a and n are constants. According to this 

 view there should not be any free toxin or antitoxin in 



