460 MICROBIOLOGY 



The receptors or side chains present in the cells may have 

 a specific affinity for a given toxin and when united with the 

 toxin the receptor loses its normal physiological function. If 

 the effect of the toxin destroys the cells further activities 

 cease, but if the effect on the cell is less severe, the reparative 

 forces presumably cause the neutralized receptor to be cast 

 off and the regenerative powers of the body cause new "re- 

 ceptors" to appear. As pointed out by Weigert 34 the re- 

 generative processes rarely stop when the tissue is replaced 

 but tend to an overproduction "the profligate habit of 

 nature" so that many receptors may be given off by the 

 cells and set free in" the circulation. These free receptors con- 

 stitute the active principle in antitoxin. They possess in this 

 free state the same specific affinity for the toxin or antigen as 

 they do when attached to the body of the cells. 



In explaining the production of antitoxins or antibodies 

 and their action on the toxins or antigens it was necessary 

 because of a lack of knowledge of their chemical nature to 

 represent graphically chemical combinations. When the 

 chemical formulae of these substances are determined the 

 graphic figures will undoubtedly be replaced by specific 

 chemical formulae. 



Ehrlich assumes that the body cells possess receptors of 

 different kinds and that the toxins or other substances that 

 come to them which have a specific affinity for any of the 

 receptors will combine with them. It is through these recep- 

 tors that the toxins come in combination with the cytoplasm 

 of the cells. 



When the toxin attacks the cell through the receptor there 

 is produced an excess of receptors which in case of excessive 

 stimulation by toxin are thrown off from the cells and circulate 

 free in the blood plasma. These free receptors possess a 

 single combining group of atoms and may combine with the 

 toxin in the circulation before it comes in contact with the 

 cells themselves. The toxoids are modified toxins which have 



^Weigert. Verhandl. d. gesund. Deut. Naturf. Aertze, Frank- 

 fort, 1896. 



