CHAPTER XII

SUMMARY AND CONCLUSIONS 285

Disharmonies in the human constitution as the chief source of our sorrows—Scientific data as to the origin and destiny of man—The goal of human existence—Difficulties in the way of scientific investigation of the problem, What is progress?—Difficulty of including the whole human rate in a scheme of progress and morality—The instincts of life and of natural death—Application to real life of the doctrines set forth in this book

ILLUSTRATIONS

Photograph of Élie Metchnikoff Frontispiece Figs. Page 1. Catasetum saccatum 24 2. Herminium monorchis 26 3. Cerceris 28 4. Listera ovata 32 5. Pelopæus 34 6. Cæcum and vermiform appendage of man 44 7. Cæcum and vermiform appendage of chimpanzee 45 8. Fœtus of gibbon 46 9. Human fœtus 47 10. Fœtus of gorilla 50 11. Human fœtus 51 12. Paramecium about to divide 230 13. Conjugation of Paramecia 231 14. Section of a renal tubule invaded by Macrophags 241 15. Brain cells devoured by Macrophags 241 16. Hair becoming grey 243 17. Chætogaster about to divide 265 18. Ephemerids 271 19. Swarms of Palingenia virgo 273 20. Larva of an Ephemerid 276

THE NATURE OF MAN