152 LIFE OF ELIE METCHNIKOFF 



their evolution entirely out of account, as well as 

 their starting-point in lower animals whilst it is 

 the very simplicity of the latter which allows us to 

 penetrate to the origin of the phenomena. 



Perhaps a general plan of the whole, in the shape 

 of a comparative study, embracing the whole animal 

 scale, would throw light over the generality of phago- 

 cytic phenomena and would make their continuity 

 understood through normal and pathological biology. 

 He determined to make this effort. In order to place 

 in a fresh light the biological evolution of phagocytosis 

 phenomena in disease, he chose one of the principal 

 manifestations of pathological phagocytosis, inflam- 

 mation, and, in 1891, gave a series of lectures on this 

 subject which he afterwards published in a volume. 

 According to his usual method, he began by the 

 most primitive beings, taking as a starting-point the 

 lower organisms which do not yet possess differentiated 

 functions, and whose normal digestion is, if necessary, 

 used as a means of defence against noxious agents. 

 Then, by a comparative study in every grade of 

 the animal kingdom, he proved that the same mode 

 of struggle and defence persists in the mesodermic 

 cells, the phagocytes in all animals in general. 

 In all of them, thanks to a special sensitiveness, 

 Chimiotaxis, phagocytes move towards the intruder, 

 to englobe it and digest it if they can. This reaction 

 for defence by the organism takes place in beings 

 endowed with a vascular system by the migration 

 of the blood-phagocytes which traverse the walls of 

 the blood-vessels in order to betake themselves to 

 the invaded point. 



In higher animals, all the symptoms which accom- 

 pany this phenomenon of defence and which constitute 



