Uselessness of the large intestine in man.—Case of a woman whose large intestine was inactive for six months.—Another case where the greater part of the large intestine was completely shut off.—Attempts to disinfect the contents of the large intestine.—Prolonged mastication as a means of preventing intestinal putrefaction 151 V LACTIC ACID AS INHIBITING INTESTINAL PUTREFACTION The development of the intestinal flora in man.—Harmlessness of sterilised food.—Means of preventing the putrefaction of food.—Lactic fermentation and its anti-putrescent action.—Experiments on man and mice.—Longevity in races which used soured milk.—Comparative study of different soured milks.—Properties of the Bulgarian Bacillus.—Means of preventing intestinal putrefaction with the help of microbes 161 PART V PSYCHICAL RUDIMENTS IN MAN I RUDIMENTARY ORGANS IN MAN Reply to critics who deny the simian origin of man.—Actual existence of rudimentary organs.—Reductions in the structure of the organs of sense in man.—Atrophy of Jacobson’s organ and of the Harderian gland in the human race 184 II HUMAN TRAITS OF CHARACTER INHERITED FROM APES The mental character of anthropoid apes.—Their muscular strength.—Their expression of fear.—The awakening of latent instincts of man under the influence of fear 191 III SOMNAMBULISM AND HYSTERIA AS MENTAL RELICS Fear as the primary cause of hysteria.—Natural somnambulism.—Doubling of personality.—Some examples of somnambulists.—Analogy between somnambulism and the life of anthropoid apes.—The psychology of crowds.—Importance of the investigation of hysteria for the problem of the origin of man 200 PART VI SOME POINTS IN THE HISTORY OF SOCIAL ANIMALS I THE INDIVIDUAL AND THE RACE Problem of the species in the human race.—Loss of individuality in the associations of lower animals.—Myxomycetes and Siphonophora.—Individuality in Ascidians.—Progress in the development of the individual living in a society 212 II INSECT SOCIETIES Social life of insects.—Development and preservation of individuality in colonies of insects.—Division of labour and sacrifice of individuality in some insects 220 III SOCIETY AND THE INDIVIDUAL IN THE HUMAN RACE Human societies.—Differentiation in the human race.—Learned women.—Habits of a bee, Halictus quadricinctus.—Collectivist theories.—Criticisms by Herbert Spencer and Nietzsche.—Progress of individuality in the societies of higher beings 223 PART VII PESSIMISM AND OPTIMISM I PREVALENCE OF PESSIMISM