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.

'Uber die Pathologische Bedeutung der Intracellularen Verduung', Fortschritte der Medizin, 1884, 17, 558–569. Trans. Alfred I. Tauber and Leon Chernyak, Metchnikoff and the Origins of Immunology (1991)