THEORIES OF IMMUNITY. 



from an animal of a different species. Such a 

 fact tends to show that complement is the same 

 in all species of animals, although there are other 

 experiments that indicate that this conclusion 

 may not be absolutely warranted. 



Still another fact that is of importance is the 

 conclusion warranted by the evidence that com- 

 plement and immune body are not produced in 

 the same quantity, which would be expected 

 from the circumstances of the case. An illus- 

 tration is furnished by the possibility of demon- 

 strating that a given quantity of a cytolytic serum 

 may destroy a given quantity of cells. . If, how- 

 ever, fresh serum be added, the same quantity of 

 the cytolytic serum will be found capable of 

 dissolving; manv times the number of cells it 

 could act upon in the first place. 



The main point of controversy is upon the 

 multiplicity of complement, but not enough evi- 

 dence is yet before us to enable us to form a 

 definite opinion upon the matter. MetchnikofF 

 takes very strong ground in the matter, and de- 

 clares that the complement exists only in the 

 cells of the body, from whence it passes into the 



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