166 



PRINCIPLES OF BACTERIOLOGY 



possesses specific affinity. Hence, the same substance which, so long 

 as it remains in the organ, attracts the toxin and makes it possible for 

 that to exert its poisonous action on the organ, this same substance 

 acts as a protection when it circulates outside of the organ; for then it 

 satisfies the affinity of the poison's haptophore group while still in the 

 blood, preventing the poison molecule from acting on the organ itself. 



FIG. 68 



Graphic representation of Ehrlich's theory of the production of antitoxin and the neutralization 

 of toxin : a, diphtheria toxin molecule ; x, toxophore atom group ; y, haptophore or combining 

 group ; b, cell receptors with affinity for diphtheria toxin ; c, other cell receptors. 



1. Cell with its receptors. Outside of cell, free toxin molecules. 



2. Toxin molecules combined with the cell receptors having affinity for diphtheria toxin. 



3. After three days, showing multiplication of cell receptors similar to those combined with toxin. 



4. After four days, excess of receptors cast off in the blood. 



5. Toxin molecule neutralized by combining with free receptors in blood of immunized animal 

 or in an animal into which blood with free receptors bad been transferred. 



In the formation of the specific antibodies we must therefore dis- 

 tinguish three stages (Fig. 68) : 



The binding of the haptophore group to the receptor (2) . 



The increased production of the receptors following this binding (3) . 



The thrusting off of these increased receptors into the blood (4). 



A considerable part of Ehrlich's theories upon toxins and antitoxins 

 have been confirmed experimentally; for example, the presence of the 

 separate toxophore and haptophore groups and the existence of atom- 

 groups with specific binding properties in all substances with which we 

 can immunize. 



