secretions of the milk glands. So are all the sons and daughters of mammals. Whether they come into the world among the waters or among the desert sands, in the hollow of a tree, in a hole in the earth, or in a palace, the children of mammals are frail and pitiful, and they survive to grow and multiply only because they are the object of the loving and incessant sacrifices of a mother. Mammals are distinguished from all other animals by the possession of two kinds of skin glands—the sweat glands and the oil glands—and by the development of certain of these glands in the female into organs for the nourishing of the young. Among reptiles and birds the lower jaw is suspended from the skull by a bone called the quadrate bone. Among men and other mammals the lower jaw is joined directly to the skull, the quadrate bone becoming, in the vicissitudes of evolution, the hammer (malleus) of the mammalian ear. Man has a four-chambered heart—two reservoirs which receive, and two pumps which propel, the scarlet waters of the body. Fishes have two-chambered hearts; frogs and most reptiles have three-chambered hearts; all mammals and birds have four-chambered hearts. The red corpuscles in the blood of fishes, frogs, reptiles, and birds, are discs, double-convex, nucleated, and in shape oval or triangular. In man and in all other mammals (except the archaic camel) the red corpuscles are double-concave, non-nucleated, and circular. ‘Man has a diaphragm dividing the body cavity into chest and abdomen, and a shining white bridge of interlacing fibres, called _corpus callosum_, uniting his cerebral hemispheres. And man is a mammal because, like other mammals, he has, in addition to the qualities already mentioned, these valuable and distinct characteristics. IV. Man a Primate.