"For example," says this distinguished Frenchman, "the union of the bones with the epiphyses takes place in the camel at eight years of age, and he lives forty years; in the horse at five years, and he lives twenty-five years; in the ox at four years, and he lives from fifteen to twenty; in the dog at two years, and he lives from ten to twelve years; and in the lion at four years, and he lives twenty. This is strongly corroborative of the correctness of the theory in relation to the longevity of man, which cannot now, I think, fail to be accepted generally." As a necessary consequence of this feature of life, assured to us by Monsieur Flourens, that able gentleman modifies seriously the different ages or stages of our existence. "I prolong the duration of infancy," he says, "up to ten years, because it is from nine to ten that the second dentition is terminated. I prolong adolescence up to twenty years, because it is at that age that the development of the bones ceases, and consequently the increase of the body in length. I prolong youth up to the age of forty, because it is only at that age that the increase of the body in bulk terminates. After forty the body does not grow, properly speaking; the augmentation of its volume which then takes place is not a veritable organic development, but a simple augmentation of fat. After the growth, or, more exactly speaking, the development in length and bulk has terminated, man enters into what I call the period of invigoration--that is, when all our parts become more complete and firm, our functions more assured, and the whole organism more perfect. This period lasts to sixty-five or seventy years, and then begins old age, which lasts for thirty years." To those who may be desirous of inquiring why it is that man, who is obviously designed to live to so great an age, so seldom attains it, Monsieur Flourens replies: "With our manners, our passions, our torments, man does not die; he kills himself!" In view of these facts, then, and of the universally received opinion that, in this day and generation, man does not live out even one-half of the years apportioned to him by the Creator of all things, is it not astonishing that physical culture and the best and surest modes of attaining health and strength, as well as this maximum of human life, do not command the first place, not only in every family, but in the councils of the nations also? The generations come and go on half time only; and that, too, under a pressure of weakness, disease, and discomfort which renders the life of millions a burden to them.