POISONING BY PLANTS. GENERAL PRINCIPLES 21 



animals, a brief statement of Ehrlich's views is given here. Ehrlich 

 reasoned that if it is by the chemical side chains of the organic molecules 

 that change in the chemical composition of toxic bodies is brought about 

 then the living cell has side-arms or receptors of the cell molecule by which 

 the haptophore (binding portion of the toxin molecule) fits "like a key 

 fits a lock." Each molecule of the animal cell has innumerable receptors 

 of which only a certain number are suitable for the anchoring of the toxin 

 molecule to the living cell. If only a few toxin molecules are united with 

 the cell receptors then the toxin is of low toxicity and the effects on the 

 cell will be slight, if more are anchored, the poisonous effects will be greater 

 or entirely destructive to the cell. Regeneration of the receptors takes 

 place, and if these are produced in such numbers by the activity of the 

 antigen, or poison, they are crowded off and find their way into the blood 

 serum, where they are capable of anchoring the toxin molecules as before 

 and thus become the antibodies, or antitoxins, which finally bring about a ' 

 neutralization of the toxin. The persistence of these antibodies (anti- 

 toxins) in the animal system produces immunization. We may summarize 

 Ehrlich's conception of the nature of toxins, as follows: Each molecule of 

 toxin consists of a great number of organic complexes grouped as in 

 organic compounds generaUy as side chains about a central radical, or 

 ring. One or more of these complexes has a chemical affinity for certain 

 chemical constituents of the tissues of animals susceptible to the toxin with 

 which the toxin molecule reunites. The toxin molecule must contain two 

 separate atom groups. One of these must possess the power of binding 

 and be stable. This is the haptophore, or anchoring group. The other 

 one by which the toxin molecule exerts its deleterious action, must be 

 more easily changed or destroyed. This is the toxophore, or poison 

 group. An animal is susceptible to a toxin only when its cells contain 

 receptive substances which possess a chemical affinity for the haptophore 

 of the toxin molecule and also substances which can be influenced harm- 

 fully by the toxophore of the same molecule. The nature of the changes 

 brought about by the toxophore of the toxin molecule is not understood, 

 but there are many resemblances to the action of enyzmes or ferments, 

 but the analogy is not complete. We find the closest analogy to the enzy- 

 mes in the toxic substances that destroy the bacteria and the red-blood 

 corpuscles (bacteriolysins and hemolysins). 



The immunity against enzymes and toxic bodies seems to have an 

 identical origin in the over production of the cellular receptors which bind 



