76 ANTIBODIES, IMMUNITY, WASSERMANN SERUM TEST 



an animal. While the latter symbol L + designates a toxin-antitoxin 

 mixture which contains one fatal dose in excess which will kill the 



f 



FIG. 33 



u 



B 



E 



--F 



Graphic representation of receptors of the first and third orders and of complement as con- 

 ceived by Ehrlich: A, complement; B, intermediary or immune body; C, cell receptor; D, part 

 of cell; E, toxophorous group of toxin; F, haptophorous group. (Park.) 



experimental animal within a few days. If a toxin is freshly prepared 

 and its minimum fatal dose ascertained it will be found that a cer- 

 tain amount of antitoxin is required to neutralize it completely. If 



100 fatal doses are taken it will require 

 FlG - 34 100 protective doses of the antitoxin to 



produce a completely neutralized mix- 

 ture (L ). However, when the toxin 

 gets older it can be shown that instead 

 of 100 protective doses only about 80 

 are required to prevent a fatal effect. 

 In the case of the fresh toxin L + minus 

 L is equal to one fatal dose; but after 

 the toxin has gotten older L + minus 

 L is equal to apparently 21 fatal doses. 

 The reason for this peculiar behavior 

 has been already explained above. The 

 toxin that is part of it has lost its 

 toxophore group, but has retained its 

 haptophore group, and with it its com- 

 bining power toward free cell receptors 

 on antitoxins. The toxin has been 

 changed into a toxoid. 



Receptors of the second order are 

 pictured in c. Here e represents the 

 haptophore group, and d the zymo- 

 phore group of the receptor, / being 

 the food molecule with which this 

 receptor combines. Such receptors 

 are possessed by agglutinins and 

 precipitins. It is to be noted that 

 the zymophore group is an integral 

 part of the receptor. (Park.) 



