RECEPTORS. 353 



5. Receptors of the second order, toxins, agglu- 

 tinins, precipitins and complements, undergo a 

 peculiar degenerative change, spontaneously or as 

 a result of exposure to injurious agents, in which 

 the toxophorous or zymotoxic group disappears or 

 is rendered inactive. The termination -oid is af- 

 fixed to the altered bodies, as toxoid, agglutinoid, 

 precipitoid and complementoid. Wechsberg has 

 described a similar degeneration of one of the hap- 

 tophores of amboceptors, calling the product am- 

 boceptoid. Toxoids and complementoids on im- 

 munization cause the formation of corresponding 

 antitoxins and anticomplements, by virtue of re^ 

 tention of their haptophorous groups. 



6. By means of a special technic devised for 

 studying the neutralization of toxin by antitoxin, 

 i. e., the partial saturation method, Ehrlich found 

 diphtheria toxin to be a very complex substance. 

 Not all the molecules of the toxin have the same 

 affinity for antitoxin, and according to the de- 

 grees of their affinity have received the names of 

 prototoxin, deuterotoxin and tritotoxin. Simi- 

 larly, protoxoids and syntoxoids are molecules of 

 toxoid having different affinities for antitoxin. 

 These conditions are represented graphically by 

 means of the "toxin spectrum" described pre- 

 viously. 



7. Ehrlich claims that the diphtheria bacillus 

 secretes two toxins, one of which causes the acute 

 manifestations of diphtheritic intoxication, where- 

 as the second toxin, i. e., toxon, has a prolonged 

 incubation period and probably causes diphtheritic 

 paralysis. Toxon has a lower affinity for diph- 

 theria antitoxin than the other constituents of the 



