Professor Metchnikoff expounds his main thesis that human life is not only unnaturally short but unnaturally burdened with physical and mental disabilities. He analyzes the causes of these disharmonies and explains his reasons for hoping that they may be counteracted by a rational hygiene.Elie Metchnikoff (1845-1916) was Sub-Director of the Pasteur Institute, and a Nobel Prize winner for medicine. Metchnikoff was born in Russia and lived in Paris from 1888, where many of his works were originally published in French. He worked in the fields of embryology, comparative anatomy, pathology, bacteriology and immunology.