TOXINS AND ANTITOXINS 267 



5. Toxin is neutralized but not destroyed by antitoxin. When 

 some batches of toxin-antitoxin mixtures are frozen, they become 

 more toxic (Banzhaf, 1928, p. 749). When a mixture of toxin- 

 antitoxin is injected into the tissues of man or any suitable ani- 

 mal, the toxin is liberated slowly and stimulates the production 

 of antitoxin. 



6. Three theories as to the mechanism involved in toxin neu- 

 tralization liy antitoxin are given. 



Elirlicli conceived of the reaction as similar to that between 

 a strong acid and a strong base. To explain many clinical and 

 experimental phenomena he postulates the secretion of two tox- 

 ins, a toxin and a toxone. These differ in their avidity for anti- 

 toxin and in the symptoms they produce. In his opinion the 

 toxone causes the late paralysis observed. He also assumes that 

 these toxins readily deteriorate into toxoids that differ in their 

 affinity for antitoxin. His conclusion that the toxic and antigenic 

 properties arc not interdependent is borne out l)y subsequent 

 work. 



A second theory is that of Arrhenius and ]\Iadscn. They re- 

 gard the reaction as similar to that between a weak acid and a 

 weak base. This theory is apparently accepted by Glenny (1931) 

 and his associates. 



A third theory is called the adsorption theory of Bordet. When 

 antitoxin is added to toxin he believes that instead of neutraliz- 

 ing a fraction of the toxin molecules present, it partly neutralizes 

 every molecule of toxin. 



According to this theory Ehrlich's toxone is only a partly neu- 

 tralized toxin. Bordet explains the zone phenomenon and the 

 "Danysz effect" from tlie standpoint of physical chemistry. 

 Wells (1929) and others seem to feel that Bordet 's theory more 

 nearly explains all of the observed phenomena than any other 

 theory. Ehrlich's original conception that it is analogous to 

 the reaction between a strong acid and a strung base seems to 

 be generally abandoned. 



7. The history of the development of passive and active im- 

 munity to diphtheria is discussed. Passive immunization is em- 

 ployed in the treatment of clinical diphtheria and to give imme- 

 diate protection to susceptible individuals who have been ex- 



