AGGLUTININS 65 



food particle. Such a receptor would then possess 

 two haptophore groups, one for the food particle, 

 the, other for the ferment-like substance. These 

 are Ehrlich's " receptors of the third order " and 

 will be discussed in the next chapter. Confining 

 ourselves for the present to the agglutinins we find 

 that the existence of the two groups (haptophore 

 and agglutinating) has experimental confirma- 

 tion. We have seen that an agglutinin may be 

 changed by the action, for instance, of acids, so that 

 it will no longer possess any agglutinating action, 

 but will still combine with the bacteria. Once the 

 agglutinating power is lost it cannot be restored, 

 in which respect the agglutinins differ from the 

 bacteriolvsins.x 



