74 ANTIBODIES, IMMUNITY, WASSERMANN SERUM TEST 



representative, have their carbon atoms arranged in a ring. Carbon 

 is a tetravalent atom, that is, each atom has four chemical affinities 

 which can be satisfied by other atoms in forming various chemical 

 compounds. The formula of benzene, which is a stable chemical 

 compound, in which all affinities are satisfied, is C 6 H 6 . Its chemical 

 structure, according to Kekule's hypothesis, is explained by assuming 

 that the tetravalent carbon atoms form a ring in which each of the 

 carbon atoms is united with one neighbor by two affinities and with 

 the other neighbor by one affinity. This leaves for each carbon 

 atom one affinity free to which the hydrogen atom is united. The 

 picture of the hypothetical benzene ring is shown in Formula A. 



H H 



H C C H H C C NH 2 



H C C H H C C H 



Formula A. Benzene. Formula B. Anilin oil. 



Each of the hydrogen atoms may be replaced by a more complicated 

 molecular group, so that we may have, for instance, a body of the 

 formula C 6 H 5 NH 2 (Formula B), or anilin oil, which is the basis of 

 all anilin stains used in pathologic and bacteriologic work. In this 

 body the group NH 2 , which is attached to one of the carbon atoms, 

 is called a side-chain. 



According to the hypothesis of Ehrlich, the chemical substances 

 of cells as well as of toxins and similar bodies contain side-chains, 

 which by uniting in the animal body produce both poisonous effects 

 and immunity. How this is accomplished according to the hypo- 

 thesis will be shown. The chemical formulae of the live cell sub- 

 stances, the toxins and the hypothetical side-chains, are not known. 

 Therefore, in order to demonstrate graphically what is supposed 

 to happen, figures which represent the matter as a simple physical 

 arrangement taking place between geometrical bodies are employed. 



Side-chains. The side-chain theory assumes that a toxin has one 

 side-chain which can attach itself to the side-chain of a cell. After 

 this has occurred another side-chain of the toxin fastens itself to a 

 second side-chain of the same cell. It is only after this second attach- 

 ment has taken place that damage is done to the cell. In other words, 

 the first side-chain only serves to anchor the toxin to the cell, and 

 the second side-chain of the toxin produces the poisonous effect. 



The four side-chains in this mutual process between the cell and 

 the toxin have received special names . 



Haptophore Group. The side-chain which simply attaches the 

 toxin to the cell. 



