INFECTION AND IMMUNITY 383 



compensate by the regenerative formation of additional 

 receptors to meet the emergency. 



The period of " reaction" following the injection of 

 the antigen corresponds to the time during which the 

 cells are thus overcoming the embarrassment and provid- 

 ing themselves with the needed receptors. As the in- 

 jections of the antigen are repeated and the doses in- 



FIG. 137. FIG. 138. 



Fios. 137, 138. The left hand figure shows a cell embarrassed by the attachment 

 of haptophorous groups: the right hand figure a cell compensating by regeneration of 

 the receptors, some of which can be seen detaching into the surrounding tissue juice. 



creased, the number of new receptors to be formed 

 becomes greater and greater, and the habit of regen- 

 erating them so effectually established that they form in 

 excess of all requirements, and being superfluous detach 

 from the cell and occur free in the lymph and blood. 

 These free receptors retain their haptophilic affinity and 

 their haptophorous adaptation, so that should adapted 

 haptophiles be present they combine with them in the 

 blood, before they are able to reach the cells, or being 

 present in the drawn blood confer upon it the future 

 power of combining with the toxin molecules rendering 

 the toxin inert when injected, after the combinations 

 have been effected, into some new animal. 



The antitoxic nature of the immune serum is thus 

 referable to the liberated superfluous receptors with 

 which the blood serum of the immunized animal becomes 



