CHAPTER X

INTRODUCTION TO THE SCIENTIFIC STUDY OF OLD AGE 228

General account of old age—Theory of senile degeneration amongst unicellular organisms—Conjugation amongst infusoria—Old age in birds and in anthropoid apes—General characters of senile degeneration—Sclerosis of the organs—Phagocyte theory of senile degeneration—Destruction of higher elements by macrophags—Mechanism of whitening of the hair—Serums acting on cells (cytotoxins)—Sclerosis of the arteries and its causation—Harm done by the microbes of the alimentary canal—Intestinal putrefaction and the modes of preventing it—Attempts to prolong human life—Longevity in biblical times