52 IMMUNITY 



In the case of toxin, the two lateral chains of its molecule are 

 called haptophores and toxophores. The haptophores seize the 

 lateral chains of the cell and the toxophores poison it. 

 | Ehrlich conceived that cells were nourished by their lateral chains, 

 each having a central nucleus with many lateral chains called recep- 

 tors bristling all over it. Complex albumins, food stuffs or poisons 

 (as the case may be) unite with it. This means a chemical union of 

 a part of a cell with all or part of a group of atoms. But certain 

 body cells are only capable of uniting with certain toxins. It is 

 known that the toxin of tetanus has a chemical affinity for the 

 nervous system and for its neural elements and not for liver or 

 spleen celLsJ 



Q]he poisons of snake venom seem incapable of uniting with 

 any cells of the pig; this animal is, therefore, immune to snake 

 venom.^ 



^yk>w, as these toxins unite with the cells by means of the receptors, 

 the cell is stimulated to produce an excessive number of these recep- 

 tors, which are cast off and become free. Nature is very prodigal 

 and whenever any of the tissues of the body have been injured, or 

 there is a deficiency, an enormous excess of reparative cells is pro- 

 ducecfj Weigert first called attention to this phenomenon, which 

 has been called Weigert' s over-production theory. Lj$o when the 

 haptophores of the toxin molecule combine with the receptors of the 

 cell, the latter are incapable of any further union and are useless to 

 the celT^ Accordingly a great number of free receptors are gener- 

 ated, and floating in the blood, engage the haptophorous portion of 

 the toxin. Thus the toxophore is neutralized and rendered innocu- 

 ous before it can reach the cell. These free over-produced recep- 

 tors constitute the anti-toxin. This is the essence of Ehrlich's 

 theory. (Fig. 17.) 



Through the process of time and oxygenation, the toxophorous 

 group in the toxin becomes innocuous, and only the haptophorous 

 group remains active; nevertheless the haptophorous group is able 

 to combine with the receptors and to stimulate the cell into generat- 



