HAMILTON SCIENTIFIC ASSOCIATION 



Metchnikoff ascribes to these cells the sole holier of providing 

 bodily immunity. They ingest and destroy the bacteria. They 

 absorb and neutralize the toxins, 



Ehrlick, on the other hand, has a more extensive and com- 

 plicated explanation of immunity which in brief is as follows : 



First, regarding antitoxms. The various body tissue cells 

 have a multitude of processes called receptors, which serve as con- 

 necting links between the cell and the other elements, such as food 

 molecules, etc. These receptors are of various kinds and can be 

 produced by the cell at will. Not only so, but under special stim- 

 ulation, eg., the presence of toxins in the system, there can be an 

 overproduction of these receptors, which, being cast off from the 

 cell into the circulation, act as an antitoxin^ combine with the 

 toxin molecule and render it inert. 



-; .ast-off Receptors or 

 »' Antitoxin 



Neutralized 



The presence of these floating receptors in the circulation after 

 an infection is over accounts for the subsequent immunity. 



Each separate toxin in the system stimulates the cell to the 

 production of its specific receptor, so that the receptors of one in- 

 fection cannot act as the antitoxin for a second different infection. 

 E.g. : An attack of measles does not immunize against an attack 

 of scarlet fever since their receptors are not alike. 



The formation and method of action of the bactericidal sub- 

 stance admits of no such simple explanation. Suppose an individ- 

 ual has become immune to an infection, say typhoid fever. Let 



