THE PROTECTIVE SUBSTANCES OF THE BLOOD 373 



is the fact that the two processes may interfere with one another; 

 a marked pathological action can diminish the regenerative process 

 or even prevent it entirely. This is shown, for example, by the fact 

 that it is almost impossible in the case of certain animals highly 

 susceptible to tetanus poison, such as mice and guinea-pigs, to pro- 

 duce antitoxin by means of unmodified poison, while the result is 

 easily attained by the use of toxoids. 



Coming now to the regenerative process, which leads to the pro- 

 duction of antitoxin, it will be found by any one familiar with the 

 fundamental principles formulated by Carl Weigert that there is 

 nothing remarkable about the process. The receptor which has 

 anchored the haptophore group of the toxin or toxoid molecule 

 becomes useless for the cell because of this occupation; it is no longer 

 able to exercise its normal function, namely, the anchoring of nutri- 

 tive substances. The cell has thus suffered a loss which must be 

 replaced. 



In such processes it is very common to find, as Weigert 's re- 

 searches have shown, that the loss is not merely replaced, but that 

 it is over compensated. The same thing takes place in the methodical 

 immunization when continued and ever increased doses of immu- 

 nizing substance are introduced. Part of the newly formed re- 

 ceptors still attached to the cell are occupied by the immunizing 

 substance only to be replaced by a regeneration greater in degree 

 than before. Owing to this increased demand the protoplasm to a 

 certain extent is trained in one direction, namely, to produce anew 

 a certain kind of constituent, the receptors in question. Finally, 

 such an excess of receptors is produced that there is no longer room 

 in the protoplasm for them. Then they are thrust off as free mole- 

 cules and pass into the body fluids. According to this view the anti- 

 toxin is nothing more than the thrust-off receptor apparatus of the 

 protoplasm, i.e., a normal cell constituent produced in excess. 



From among the many facts already at hand I shall select merely 

 a few to serve as proof of the correctness of this hypothesis, this 

 "side-chain theory," as it is called. 



The first point deals with the demonstration in normal tissues 

 of the toxinophile receptors assumed by the theory. Although such 

 an anchoring of the poison by the organs had already been demon- 

 strated by the clinical course of the poisoning and by Donitz's thera- 

 peutic experiments on animals poisoned with tetanus and diphtheria 

 poisons, it remained for Wassermann to show that certain body 



