ANTITOXINS 



stance benzene is made up of atoms of carbon and 

 hydrogen which are assumed to be arranged in 

 relation to each other as follows: 



Any substance which acts on benzene may re- 

 place any one or more of the H's with another 

 group of atoms, for instance: toluene is produced 

 by substituting CHs for one of the H's. In this 

 case the CHa is considered to be a side-chain, the 

 central chemical nucleus remaining unchanged. Ehr- 

 lich assumed that a cell is nourished or injured only 

 by substances which possess atom groups arranged 

 chemically in such a manner as to be able to form a 

 side-chain fitting that particular cell. 



Originally the side-chain theory was applied by 

 Ehrlich only to the production of the specific anti- 

 toxins, i.e., substances in the blood, which act not 

 only on the living bacteria, but also and especially 

 on their dissolved toxins. Later on he extended it 

 so as to apply also to the formation of specific bac- 

 tericidal and haemolytic substances in the serum of 



