lungs, and that which passes out, are the same in bulk--plus watery vapour--although what enters is pure air, and what is expelled, is loaded with carbonic acid. The blood, having exchanged carbonic acid for oxygen, is now altered from a black to a bright scarlet colour, and is in a condition to be circulated through the system. On leaving the lungs by the "pulmonary veins," it enters the left auricle of the heart, and passes from thence to the left ventricle, which is very powerful, and forces it by compression upwards into the "aorta" (the first great artery), and thence through the other arteries, which divide, and become smaller and smaller until it arrives at every part of the body, forming a network of fine vessels which are called capillaries; so perfectly are these vessels distributed, that it is almost impossible to cut or prick any part of the body without wounding one of them, and thereby drawing blood. When these capillaries have supplied this pure blood to repair and renovate every part of the system, and received for the new material, that which is worn out or spoiled, they urge it onwards to where they unite into small veins, and, as these continue to unite, they form large trunks, and pour the blood, now black and impure, into the right auricle of the heart, together with the fresh material (chyle) derived from the food, again to be sent through the lungs and purified for fresh circulation. This description applies as well to the other Mammalia as it does to Man, for these classes do not differ from Man in their physical structure, except in form and size, and the alteration in the proportion of the various parts to adapt each to its peculiar purpose. [Illustration: EUROPEAN AND NEGRO.] MAN is, without doubt, the only animal possessed of reflective and reasoning faculties, and the possession of these has raised him immeasurably above all the rest. He has also physical capabilities suitable to a dominant being whose race is destined to people the earth in every part. Were his constitution formed like that of the Chimpanzee or the Ourang, he could only live in the very hottest of climates; but it is found that Man is healthy and happy through ranges of temperature, which would prove fatal to most other animals. In the frigid regions of the north, the Laplander enjoys many comforts which he fancies could never be obtained in any other latitude, and the Bushman of Africa, following the wild animals of that region, and needing no covering to shield him from the burning rays of the sun, deems his lot the happiest that can be. The human race are gradually increasing in number, and there is scarcely a spot capable of being inhabited at all, but they are found there; and, wherever Man comes, the wild animals of the region retire or become entirely extinct, excepting those which serve him as food, such as the Ruminants.