Man is a _primate_. There are four divisions in the order of primates—lemurs, monkeys, apes, and men. But the most interesting and important of these, according to man, is man. Man is a primate because, like other primates, he has arms and hands instead of fore-legs. And these are important characteristics. It was a splendid moment when the tendencies of evolution, pondering the possibilities of structural improvement, decided to rear the vertebrate upon its hind-limbs, and convert its anterior appendages into instruments of manipulation. So long as living creatures were able simply to move through the airs and waters of the earth and over the surface of the solids, they were powerless to modify the universe about them very much. But the moment beings were developed with parts of their bodies fitted to take hold of and move and fashion and compel the universe around them, that moment the life process was endowed with the power of miracles. With the invention of hands and arms commenced seriously that long campaign against the tendencies of inanimate nature which finds its most marvellous achievements in the sustained and triumphant operations of human industry. None of the primates excepting man use their hind-limbs as a sole means of changing their place in the universe, but in all of them the fore-limbs are regularly used as organs of manipulation. Man is a primate because his fingers and toes, like those of other primates (except the tiny marmosets of Brazil), end in nails. Man has neither claws to burrow into the earth, talons with which to hold and rend his victims, nor hoofs to put thunder into his movements. The human stomach, like that of all the other primates, is a bagpipe. The stomach of the carnivora is usually a simple sack, while rodents have, as a rule, two stomachs, and ruminants four. Man is a primate because his milk glands are located on the breast and are two in number. The mammary glands vary in number in the different orders of mammals, from two in the horse and whale to twenty-two in some insectivora. Most ruminating animals have four, swine ten, and carnivora generally six or eight. These glands may be located in the region of the groin, as in the horse and whale; between the forelimbs, as in the elephant and bat; or arranged in pairs extending from the fore to the hind limbs, as in the carnivora and swine. In man and all other primates (except lemurs) the mammary glands are pectoral and two in number. All primates, including man, have also a disc-shaped placenta. The placenta is the organ of nutrition in mammalian embryos. It is found in all young-bearing animals above the marsupials, and consists of a mass of glands between the embryo and the parental body. In some animals it entirely surrounds and encloses the embryo; in others it assumes the form of a girdle; and in still others it is bell-shaped. The primates are the only animals in which this peculiar organ is in the shape of a simple disc.[1]