a series of prescriptions by which the author fancies that life may be lengthened and the evils of old age swept from our path. The dangerous flora must be transformed into a cultivated and selected flora. Although the organ in question may be of doubtful utility, and although its existence, the legacy of atavic heredity, must be considered as a disharmony of human nature, Metchnikoff does not go so far as to propose that it should be cut away, and that we should call in surgery to assist in making mankind perfect! But the rational means he proposes will be endorsed by the most judicious students of hygiene; and their effect, if it is not as wonderful as one hopes for, cannot fail to ameliorate the conditions of old age and make it more vigorous. § 3. DISHARMONIES IN HUMAN NATURE. Another misery in the condition of man is due to the dissidencies of his nature—that is to say, to his physical imperfections and the discordancies which exist between the physiological functions and the instincts which should regulate them. This discordance reigns throughout the physical organism. The body of man is not the perfect masterpiece it was once supposed to be. It is encumbered with annoying inutilities, with rudimentary organs that have neither rôle nor function, unfinished sketches which nature has left in the different parts of his body. Such are the lachrymal caruncle, a vestige of the third eyebrow in mammals; the extrinsic muscles of the ear; the pineal gland of the brain, which is only the rudiment of an ancestral organ; the third eye, or the Cyclopean eye of the saurians. The list is interminable. Wiedersheim has counted in man 107 of these abortive hereditary organs, the useless vestiges of organs useful to our remote animal ancestors, atrophied in the course of ages in consequence of modifications that have taken place in the external medium. These rudimentary organs are not only useless; they are often positively harmful. But the most serious discordance is that which exists between the physiological functions and the instincts which regulate them. In a well-regulated organism slowly developed by adaptation the instincts and the organs alike should be in relation with the functions. All really natural acts are solicited by an instinct, the satisfaction of which is at once a need and a pleasure. The maternal instinct is awakened at the proper moment in animals, and it disappears as soon as the offspring requires no more assistance. A craving for milk is shown in all newborn children, and often disappears at an early age.