182 A MANUAL OF BACTERIOLOGY 



being accidental. On this assumption the difficulty is 

 obviated of supposing that special chemical groups or 

 molecules exist preformed for the special purpose of 

 combining with different toxins and for no other function. 

 Moreover, small amounts of anti-bodies, such as antitoxin, 

 bacteriolysin, agglutinin, etc., are met with in normal 

 untreated animals and in man. While some have sup- 

 posed that the small amount of diphtheria antitoxin 

 (equivalent to half a unit or so) present in human blood- 

 serum is due to an infection with the diphtheria bacillus 



FIG. 28. Second stage in anti- FIG. 29. Third stage in anti- 



toxin formation. (After toxin formation. Side-chains 



Ehrlich.) beginning to be produced in 



excess. (After Ehrlich.) 



(not necessarily an attack of diphtheria), it seems more 

 reasonable to suppose that this antitoxin is due to a 

 natural liberation of such side-chains from the protoplasm 

 and that artificial antitoxin production is merely a very 

 great stimulation of this natural process. 



The toxin molecule, according to Ehrlich, possesses at 

 least two fixative atomic groups or side-chains. One of 

 these, the " haptophore group," conditions the union 

 of the toxin molecule with cell-protoplasm ; the other, 

 the " toxophore group," conditions its toxic action. 

 Similarly, in order that the cell may suffer the full effect of 



