1.
There is only one constant element in immunity, whether innate or acquired, and that is phagocytosis. The extension and importance of this factor can no longer be denied.
Elie Metchnikoff
2.
Needless fear and panic over disease and misfortune that seldom materialize are simply bad habits. By proper ventilation and illumination of the mind it is possible to cultivate tolerance, poise and real courage.
Elie Metchnikoff
3.
In the same way that plants will not grow on soil that lacks some substance indispensable to their growth, so microbes, these microscopic plants which cause infectious disease, are unable to grow in an organism which does not give them all the substances they need.
Elie Metchnikoff
4.
It is possible to state as a general principle that the mesodermic phagocytes, which originally (as in the sponges of our days) acted as digestive cells, retained their role to absorb the dead or weakened parts of the organism as much as different foreign intruders.
Elie Metchnikoff