In embryos the rate of growth is still more rapid. The increase in the guinea pig in the first five days is 3,520 per cent, or an average of 704 per cent daily. From the fifteenth to the twentieth day it is 1,058 per cent, or an average of 212 per cent per day. Thus the rate of growth during the foetal period is far more rapid and it is more so in the earlier than in the later stages of embryonic development. The farther back we go, the more rapid is this rate. Thus his curves show a very steep decline in the rate of growth, even in its earlier stages, and this decline continues, although at an ever decreasing rate, to the end. Thus from this point of view the younger creatures are, the more rapidly they are dying. The weight of a fertilized germ he estimates at 0.6 milligram (and he tells us that 50,000 of these could go by mail for a two-cent stamp). Thus the human embryo at birth has increased 5,000,000 per cent of its initial weight. Old age is merely the later result of changes that have gone on at a diminishing rate ever since the ovum from which we originated was fertilized. Life is growth; the retardation of growth is old age; and its cessation is death. “Senescence is at its maximum in the very young stages, and the rate of senescence diminishes with age” (p. 250). The embryo in its earliest stages rushes toward old age at an almost inconceivable velocity, the new-born infant runs, the child walks rapidly, youth saunters, the adult mopes, and old age only crawls on toward death. In other words, the momentum of life given by impregnation at the age of zero is retarded--most at first and with a diminishing rate at every stage. Something like this same paradoxical law holds, Minot believed, for the human brain and mind. In one of his Harvey lectures he tells us that the brain of a child at birth is but little differentiated. During the first year it learns all the great adaptations in the physical and human world: time, space, ego, etc. “It learns more during the first year than in all the subsequent years of life” and from birth on the power of learning is rapidly diminished. It declines very fast during infancy, more slowly in childhood, etc.