ANTITOXINS AND RELATED ANTIBODIES 133 



sidered in this manner, as being of different types, each one capable 

 of uniting with some food substance probably only one. To take 

 up the variety of substances necessary for cell life and activity, 

 it is evidently necessary that there should be a multiplicity of 

 these receptors, and their action must be considered as very specific. 



It is found convenient to represent these cell receptors in a 

 diagrammatic form. Such is scarcely necessary in a consideration 

 of antitoxin, but will be found very helpful in a discussion of the 

 more complex antibodies. 



Ehrlich's Theory of Antitoxin Production. As has been stated 

 previously, toxins are believed to combine with the tissue-cells 

 before the latter can be injured. This union of toxin with the 

 cell takes place through the medium of the cell receptors, some of 

 which are thus diverted from their normal functions. As a result, 

 if the cell is not too seriously injured by the toxin, it or the neigh- 

 boring cells produce an increased number of receptors of the type 

 thus used. This is in accordance with the general hypothesis 

 enunciated by Weigert, that injury or irritation always results in 

 an overgrowth of tissue a hypercompensation. For example, 

 rubbing the skin will produce a callus, leaky heart valves cause 

 hypertrophy of the heart, and the cicatricial tissue of a newly 

 healed wound is generally greater in amount than the tissue it 

 replaces. These receptors are, therefore, produced in great 

 numbers, and many are eventually displaced and escape into the 

 cell-plasma and finally into the blood-stream. These freed cell 

 receptors still retain their affinity for the toxin and constitute the 

 antitoxin molecules of the serum. For each of the statements just 

 made there seems to be a good proof. That the toxin actually 

 unites with the body-cells has been shown by experiment, for 

 example, the brain tissue of an animal mixed with tetanus toxin 

 will absorb the latter and remove it from the solution, so that 

 it is without effect when injected into animals. That there is an 

 actual increase in the number of cell receptors may be shown by 

 injecting a small amount of toxin into an animal, and before anti- 

 toxins have appeared in the blood, injecting more toxin. The 

 response to the second injection will be quicker than to the first, 

 and the animal will succumb to what is not ordinarily a fatal 

 dose. This indicates an increased power of fixation for the toxin, 



