Note 77 — Chapter IV
Reading edition
The subject is not so far removed from direct human interest as one might suppose. For many years Metchnikoff, in Paris, has been studying the bacterial flora of the human intestines. His theory is, that old age is caused by the poisonous products of these intestinal bacteria, and he proposes to counteract the effects of these poisonous organisms, by introducing into the system large quantities of lactic acid bacteria, either in the form of tabloids, or in the form of sour milk cultures.