As the bones, the cartilages, the muscles, and all the other parts of the body, are naturally softer in women than in men, they do not acquire so soon that hardness which hastens death. Women, therefore, ought to live longer than men. This is actually the case; for by consulting the tables which have been formed respecting the duration of human life, we shall find that, after a certain age, women have a greater chance for long life than men of the same number of years. From this it may also be inferred, that such men as are weak in appearance, and whose constitution rather resembles that of women, have a probability of living longer than those who seem to be more strong and robust; as likewise, that in either sex such persons as have been slow in their advances to maturity, will be slow in their advances to the infirmities of old age, because in both cases, the bones, the cartilages, and all the fibres, require a longer time to arrive at that degree of solidity, which must be the foundation of their destruction. This natural cause of death is common to all animals, and even to vegetables. An oak only perishes because its more ancient parts, which are in the centre, become so hard and so compact, that they can no longer receive any nourishment; and the moisture they contain, being deprived of circulation, becomes corrupted, and gradually alters the fibres of the wood, which become red, and at length crumble into dust. The duration of life may be determined, in some measure, by the time that was employed in the attainment of maturity. A tree, or an animal, which takes but a short time to finish its growth, perishes much sooner than those which are longer in coming to maturity. Neither animals nor plants begin to spread in bulk till they have acquired their summit of height. Man grows in stature till the age of 17 or 18; but his body is not completely unfolded in all its parts till that of 30; while a dog is at its full length in one year, and at its full thickness in another. The man whose growth is so tedious, lives for 90 or an 100 years; whereas the dog seldom survives its 10 or 12th year. To the generality of other animals this observation is equally applicable. Fishes, whose growth continues for a number of years, live for centuries; and this from no other known certain cause, but the particular constitution of their bones, which do not admit of the same solidity as the bones of terrestrial animals. Whether there are any exceptions to this kind of rule, which Nature seems to have adopted in proportioning the duration of life to that of the bodily growth, we shall enquire when we come to the particular history of animals, as also whether crows and stags live for such a number of years as is commonly pretended. In the mean while, as a general truth, let it be remarked, that large animals live longer than small ones, and this because they require a longer time to come to maturity.