ÉLIE METCHNIKOFF
"As lactic fermentation serves so well to arrest putrefaction in general, why should it not be used for the same purpose within the digestive tube?"
Élie Metchnikoff (1845-1916), born Ilya Ilyich Mechnikov near Kharkov, was a zoologist and immunologist who joined the Pasteur Institute in 1888 and became its deputy director. His 1908 Nobel Prize, shared with Paul Ehrlich, recognized his work on phagocytosis and cellular immunity; that work is not in question here. The disconfirmed item is the separate longevity programme he set out from a 1904 public lecture on old age and in The Nature of Man (1903) and The Prolongation of Life (1907 French; 1908 English): the theory that the large intestine is a source of life-shortening autointoxication and that daily soured milk, carrying lactic-acid bacteria, would arrest it. The publicly_disconfirmed status applies to this longevity theory, not to his immunology. The key quotation is the analogical step on which the therapy turned, from food preservation to the gut (The Prolongation of Life, 1908, p. 166). Metchnikoff promoted the regimen on his own scientific authority; the controlled human evidence for life extension was never produced, and the autointoxication premise was rejected within a decade of his death.