1 86 MANUAL OF BACTERIOLOGY. 



right we see a free receptor (antitoxin) and one which has 

 united with toxin to neutralize it. 



The chemical nature of this conception may be illustrated 

 by recalling the formula of a molecule of benzol. Here one 

 or more H atoms may be replaced with equivalent groups 

 making phenol, salicylic acid and other derivatives. 



As the side-chains or receptors of the protoplasm are 

 essential to its existence, their combination with the toxin, 

 through its haptophore, might result in destruction of the 

 molecule. But if the damage be not too serious, the proto- 

 plasm may be stimulated to produce numerous similar side- 

 chain groups. Not all of these are necessary for the per- 

 formance of its functions, and the superfluous ones are 

 thrown off into the surrounding serum. It is well known 

 that many cells of the body exhibit analogous heightened 

 activities under stimulating influences. Such free side- 

 chains or receptors may combine with the haptophorous 

 groups of the toxin, when it will no longer be able to com- 

 bine with the protoplasm. Thus they act as a kind of buffer 

 in protecting the protoplasm from the attacks of the toxins. 

 They constitute the antitoxic part of the serum. 



Numerous experiments have been made which illustrate 

 the probable chemical nature of antitoxic action. A fatal 

 dose of diphtheria or tetanus toxin may be neutralized out- 

 side of the body by mixing it with its appropriate antitoxin. 

 Injection of the mixture shows it to be innocuous to animals. 



The manner in which toxins combine with protoplasm has 



