THEORIES OF IMMUNITY. 



Chemiotaxls: the property of certain cells of 

 being attracted towards (positive) or re- 

 pelled from (negative) foreign bodies, such 

 as bacteria, or irritant substances. 



Complement : first conceived by Ehrlich, in an 

 extension of his antitoxine theory, to ac- 

 count for the facts in immunity against 

 infection. Exists normally in serum and is 

 destroyed after an exposure of one-half 

 hour to 55° C. Must act with the immune 

 body to produce hemolysis, bacteriolysis, 

 etc. Contains two atom-groups of affini- 

 ties, one binding it to the immune body, 

 the other exerting the active lysin action 

 (hemolysis, bacteriolysis, etc.) ; this cor- 

 responds to the toxophorous atom-group in 

 the toxines. Perhaps the same as alexines 

 of Bordet. 



Cytase : Metchnikoff's term for the substance 

 existing in the phagocytes, which acting 

 through, or with the immune body, destroys 

 the bacteria. It is single of its kind ; cor- 

 responds to the complement of Ehrlich, 

 except that the latter is said to be of many 

 kinds and to exist in the blood stream. 



113 



