574 BACTERIOLOGY. 



has beeD rendered immune, to protect the normal tissues 

 from its hurtful action. 



According to the nature of the irritant from which 

 the animal has been immunized, the " receptor " is con- 

 ceived to be either of simple or complex construction, 

 and its protective function to be performed in either a 

 comparatively simple or in a more or less complicated 

 and roundabout manner. 



As a result of his studies of toxins, Ehrlich reached 

 the conclusion that they are composed of at least two 

 functionally distinct atom-groups : the one, a " hapto- 

 phore " group, characterized by its combining tendencies ; 

 the other, a "toxophore" group, distinguished for its 

 intoxicating powers ; and that for the exhibition of its 

 hurtful characteristics a toxin molecule needs to be first 

 anchored, so to speak, to the susceptible tissue by the 

 " haptophore " group, after which its intoxicating char- 

 acteristics are exhibited by the " toxophore " group. He 

 conceives the " receptors " to be likewise provided with 

 " haptophore " groups that pair with the corresponding 

 " haptophores " of the poison to which the animal is 

 susceptible or from which it has been immunized. Where 

 immunization has been induced against such relatively 

 simple substances as toxins, ferments, and certain cell 

 secretions, the " receptors " and their functions are com- 

 paratively simple i. e., the single haptophore of the 

 simple receptor pairs with that of the intoxicant and a 

 physiologically inert complex results. He conceives 

 antitoxins to be simple receptors of this type, and 

 believes the neutralization of toxins by them to take 

 place in this manner. On the other hand, if the im- 

 munization of an animal is accompanied by an acquired 

 power on the part of its serum to disintegrate bacteria, 



