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CONTENTS
EDITOR'S INTRODUCTION
PREFACE
PART I
THE INVESTIGATION OF OLD AGE
I
THE PROBLEMS OF SENILITY
Treatment of old people in uncivilised countries.-Assassination
of old people in civilised countries.-Suicide of old people.—
Public assistance in old age. Centenarians.-Mme.
Robineau, a lady of 106 years of age.-Principal characters
of old age.-Examples of old mammals.-Old birds and
tortoises. Hypothesis of senile degeneration in the lower
animals
PAGE
V
ix
II
THEORIES OF THE CAUSATION OF SENILITY
Hypothesis of the causation of senility.-Senility cannot be
attributed to the cessation of the power of reproduction of
the cells of the body.-Growth of the hair and the nails in
old age. Inner mechanism of the senescence of the tissues.
-Notwithstanding the criticisms of M. Marinesco, the
neuronophags are true phagocytes.-The whitening of hair,
and the destruction of nerve cells as arguments against a
theory of old age based on the failure of the reproductive
powers of the cells.
. 15
III
MECHANISM OF SENILITY
Action of the macrophags in destroying the higher cells.—
Senile degeneration of the muscular fibres.-Atrophy of the
skeleton.-Atheroma and arterial sclerosis.-Theory that
Old Age is due to alteration in the vascular glands.-
Organic tissues that resist phagocytosis
PART II
LONGEVITY IN THE ANIMAL KINGDOM
THEORIES OF LONGEVITY
Relation between longevity and size.-Longevity and the period
of growth.-Longevity and the doubling in weight after
birth.-Longevity and rate of reproduction.-Probable rela-
tions between longevity and the nature of the food.
Longevity in the lower animals.-Instances of long life in sea-
anemones and other vertebrates.-Duration of life of insects.
-Duration of life of "cold-blooded " vertebrates.- Dura-
tion of life of birds.-Duration of life of mammals.—
Inequality of the duration of life in males and females.-
Relations between longevity and fertility of the organism.
THE DIGESTIVE SYSTEM AND SENILITY
25
39
47
Relations between longevity and the structure of the digestive
system. The cæca in birds. The large intestine of mam-
mals.-Function of the large intestine.-The intestinal
microbes and their agency in producing auto-intoxication
and auto-infection in the organism.-Passage of microbes
through the intestinal wall . 59
IV
MICROBES AS THE CAUSE OF SENILITY
Relations between longevity and the intestinal flora.-Rumi-
nants. The horse.-Intestinal flora of birds.-Intestinal
flora of cursorial birds.-Duration of life in cursorial
birds. Flying mammals.-Intestinal flora and longevity
of bats. Some exceptions to the rule.-Resistance of the
lower vertebrates to certain intestinal microbes
73
DURATION OF HUMAN LIFE
Longevity of man.-Theory of Ebstein on the normal duration
of human life.-Instances of human longevity.—Circum-
stances which may explain the long duration of human life
PART III
INVESTIGATIONS ON NATURAL DEATH
NATURAL DEATH AMONGST PLANTS
Theory of the immortality of unicellular organisms.-Examples
of very old trees.-Examples of short-lived plants.-Pro-
longation of the life of some plants.-Theory of the natural
death of plants by exhaustion.-Death of plants from auto-
intoxication
84
94
NATURAL DEATH IN THE ANIMAL WORLD
Different origins of death in animals.-Examples of natural
death associated with violent acts.-Examples of natural
death in animals without digestive organs.-Natural death
in the two sexes.-Hypothesis as to the cause of natural
death in animals
109
Natural death in the aged.-Analogy of natural death and
sleep.-Theories of sleep.-Ponogenes.-The instinct of
sleep. The instinct of natural death.-Replies to critics.-
Agreeable sensation at the approach of death.
PART IV
119
SHOULD WE TRY TO PROLONG HUMAN LIFE?
THE BENEFIT TO HUMANITY
Complaints of the shortness of our life.-Theory of "medical
selection " as a cause of degeneration of the race.--Utility
of prolonging human life
132
SUGGESTIONS FOR THE PROLONGATION OF LIFE
Ancient methods of prolonging human life.-Gerokomy.-The
"immortality draught " of the Taoists.-Brown-Séquard's
method. The spermine of Poehl.-Dr. Weber's precepts.-
Increased duration of life in historical times.-Hygienic
maxims. Decrease in cutaneous cancer
DISEASES THAT SHORTEN LIFE
Measures against infectious diseases as aiding in the prolonga-
tion of life.-Prevention of syphilis.-Attempts to prepare
serums which could strengthen the higher elements of the
organism
136
145
INTESTINAL PUTREFACTION SHORTENS LIFE
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 com-
pletely shut off.-Attempts to disinfect the contents of the
large intestine.-Prolonged mastication as a means of pre-
venting intestinal putrefaction
LACTIC ACID AS INHIBITING INTESTINAL PUTREFACTION
151
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
RUDIMENTARY ORGANS IN MAN
Reply to critics who deny the simian origin of man.-Actual
existence of rudimentary organs.-Reductions in the struc-