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PHARMACEUTICAI, BACTERIOLOGY. 



An antigen is a toxin, of bacterial or other origin, which has the power 

 when introduced into the body, of inducing the formation of specific anti- 

 bodies. Not all toxins or poisons have this power. For example, strychnin 

 and the toxin of tetanus produce similar physiologic effects, but only the 

 latter is capable of producing an antibody. Ehrlich explains this difference 

 by assuming that strychnin and most other vegetable poisons enter into a 

 loose combination with the cell plasm, analogous to an aniline dye which 

 can be readily dissolved out again; whereas the toxin is firmly bound 

 to the cell, representing in a measure a toxic food-stuff in chemical 



Fig. 54. — Illustrating cell receptors of the first cider. A cell receptor (a) uniting 

 with the haptophore (c) of the toxin molecule or antigen. The toxin molecule or antigen 

 consists of the haptophore and the toxophore. The toxpphore produces the toxic effects 

 upon the cell, e is the haptophore of the cell receptor which has the power of combin- 

 ing with the toxin molecule thus neutralizing its possible toxic effects. Free-cell re- 

 ceptors constitute the antibodies, and are ever ready to combine with antigens or toxins, 

 should any be present. Cell receptors and antigen bodies are specific in action. The 

 haptophore of the diphtheria cell receptor does not fit the haptophore of tetanus, for ex- 

 ample. Each antigen or toxin reacts with the antibodies fitted to it. {Journal of the 

 American Medical Association, 1905, p. 9SS-) 



union with and assimilated by the cell. The atomic combination of 

 the toxin antigen, which represents this chemical union is designated 

 the haptophore group, while the atomic combination of the cell-plasm 

 with which the haptophore group unites is called the cell receptor 

 group. The haptophore group is distinct from the atomic group which 

 produces the toxic or pathologic effects, designated as the toxophore 

 group. These two groups of the antigen (toxin), namely, the hapto- 

 phore group and the toxophore group, act independently of each 

 other and possess different properties. The toxophore group is easily 



