H&MOLYSINS. 21 



can hardly be called a poison, but which still 

 possesses the power to combine with antitoxin, 

 Ehrlich calls a toxoid. Toxoids may be produced 

 spontaneously in old poisons through decomposi- 

 tion of the poison molecule, or they may be pro- 

 duced artificially by causing certain destructive 

 agents such as heat or chemicals to act on bacterial 

 poisons. The toxophore group is a very delicate 

 one and much more readily decomposed than the 

 combining (haptophore) group. Ehrlich reasoned 

 that in order for a poison to be toxic to an organ- 

 ism, i.e., in order that the toxophore group be able 

 to act destructively on a cell, it is necessary for the 

 haptophore group of the poison to combine with 

 the cell. "In every living cell," Ehrlich says, 

 " there must exist an active central body [Leistungs 

 Kern] and a number of other chemical groups or 

 side-chains. These groups have the greatest vari- 

 ety of function, but especially those of nutrition 

 and assimilation." 



The side-chains, then, according to this author, 

 are able to combine with the greatest variety of 

 foreign substances and convert these into nourish- 

 ment suitable to the requirements of the active 

 central body. They are comparable to the pseudo- 

 podia of the lower animals, which engulf food par- 

 ticles and assimilate the same for the immediate 

 use of the organism. In order that any substance 

 may combine with these side-chains it is necessary 

 that certain very definite relations exist between 



