162 LIFE OF ELIE METCHNIKOFF 



ended by disappearing entirely within them, and the 

 rabbit remained safe and sound. On the other hand, 

 it died if the same doses of the same salt had been 

 protected from the leucocytes by an elderberry bag, 

 or when the leucocytes had been attracted elsewhere 

 by a previous injection of carmine for instance. 

 Those experiments removed all doubts as to the 

 share of the phagocytes in the destruction of mineral 

 poisons. 



Certain experiments on microbian poisons spoke 

 in the same sense. Thus MM. Roux and Borrel had 

 observed that the diphtheritic toxin, which is in- 

 offensive to rats even in large doses, kills that animal 

 if a small quantity of it is introduced into the brain, 

 the probable explanation being that, in cases of sub- 

 cutaneous injections, the poison, "phagocyted" on the 

 way, was destroyed before it reached the nerve cells. 



Thus experiments seemed to plead in favour of 

 the view that the part played by phagocytosis is not 

 limited to the struggle against microbes, but also 

 extends to the defence against poisons and toxins. 



After having studied the mode of destruction of 

 these, Metchnikoff wished to elucidate the origin of 

 the counter-poisons, the specific antitoxins discovered 

 by Behring in the humors of immunised organisms, 

 a question of which the study was even more difficult. 



Metchnikoff began by asking himself whether the 

 microbes themselves did not produce antitoxins in 

 order to defend themselves against enemy micro- 

 organisms. He made many experiments but only 

 obtained negative results, and concluded that the 

 antitoxins must be manufactured by the organism 

 itself. 



