Monkeys and man differ from most mammals in so far as they possess a long duration of life, although their large intestines are very capacious. I have been unable to get exact information as to the longevity of monkeys, but I understand that these animals live longer than domesticated mammals, such as the ox, sheep, dog, and cat. Anthropoid apes are supposed to be able to reach the age of 50 years. The only other mammal with a longevity similar to that of the elephant is man. V DURATION OF HUMAN LIFE Longevity of man—Theory of Ebstein on the normal duration of human life—Instances of human longevity—Circumstances which may explain the long duration of human life Man has inherited from his mammalian ancestors his organisation and qualities. His life is notably shorter than that of many reptiles, but longer than that of many birds and most other mammals. None the less he has inherited a capacious large intestine in which a most abundant intestinal flora flourishes. Gestation and the period of growth are long in the human race, and from the point of view of theoretical considerations, human longevity should be longer than it generally is. Haller, a distinguished Swiss physiologist of the 18th century, thought that man ought to live to 200 years; Buffon was of the opinion that when a man did not die from some accident or disease he would reach 90 or 100 years. According to Flourens, man takes 20 years to grow and ought to live 5 times 20, that is to say, 100 years. The actual longevity is much below these figures, which are based on theory. I have shown, moreover, that even if the rule based on the theory of growth can be accepted as generally true, it cannot be applied in every case, as the factors controlling duration of life are very variable. Statistics show that the highest human mortality occurs in the earliest years of life. In the first year after birth alone, one quarter of the children die. After this period of maximum mortality, the death-rate slowly falls until the age of puberty, and then rises again slowly and continuously. It reaches a second maximum between the ages of 60 and 75, and then slowly falls again to the extreme limit of longevity. Bodio,[61] an Italian man of science, holds the view that the great mortality of infants is a natural adaptation to prevent too great an increase of the human race. This view, however, cannot be supported, and rational hygiene readily brings about a great diminution in the mortality of children. The cause of mortality is in most cases maladies of the intestinal canal, produced by erroneous diet, and with the advance of civilisation, infant mortality has been very greatly reduced.