LIFE OF ELIE METCHNIKOFF 279 



in the higher animals are accompanied by inflam- 

 mation and provoked by microbes, it was chiefly 

 against these microbes that our defensive cells had 

 to struggle. He named the defensive cells phagocytes. 



He confirmed his hypothesis by another observa- 

 tion, equally simple. In a little transparent crusta- 

 cean (Daphnia) infected by a small parasitic fungus, 

 (Monospora bicuspidata), he was easily able to 

 observe the struggle between the animal's mobile cells 

 and its parasites. 



These two simple observations served as founda- 

 tion and supports to the bridge by which Metchnikoff 

 connected normal biology with pathological biology. 

 Having entered the domain of the latter, he studied 

 various microbian diseases, and asked himself why 

 the organism was sometimes liable and sometimes 

 refractory. In order to elucidate this question, he 

 turned again to lower animals, in which he could easily 

 observe the most intimate phenomena, simplified. 



He ascertained that liability in an animal corre- 

 sponded with the fact that microbes introduced into 

 the organism remained free and invaded it, whilst 

 immunity coincided with the inclusion and digestion 

 of the microbes by phagocytes. 



He also found that, in artificial immunity, the 

 phagocytes are accustomed gradually, by preventive 

 inoculations, to digest microbes and their toxins. 



Thus he established the fact that phagocytosis 

 and inflammation are curative means employed by 

 the organism. 



All his ulterior researches, his studies on the 

 various categories of phagocytes and their properties, 

 on their digestive liquids, on the formation of anti- 

 toxins, on the different properties acquired by the 



