There are _motions of the heart and arteries_, which urge the blood out to the extremities and diffuse it through every part of the system, and also _motion of the blood in the capillaries_, by which the blood is circulated through the tissues, that the latter may be built up from its nutritive constituents. Then there is the _motion of the vital current_ in the veins returning towards the heart, and urged forward by the muscular and pump-like action of the chest and abdominal walls. The peristaltic _motions of the stomach and bowels_ urge onward digesting materials, exposing them successively to different solvents and aiding the absorption of nutritive matter. No less essential to life and health are numerous other minute operations or _motions_, on which vital power in all its manifestations of muscular and nervous energy depends. Many other _motions_ are consequent upon decay, growth, and repair. Oxygen, carbonic acid, watery vapors, and other gaseous matter are constantly being exchanged between the system and atmosphere. Then, the human system being a complex, chemical laboratory, there are _motions consequent upon chemical action_, constantly going on within it. _Muscular motion_, under the direction of the will, is also absolutely necessary for the maintenance of good health. Animal heat and muscular and nervous power are dependent upon motions of the minutest particles composing the body. The body is composed of fluid and semi-fluid matter, permitting great freedom of motion. Health requires that there shall be _a constant change of place_, an active transmission of material to and from vital organs and parts, through the medium of blood-vessels, as well as outside such vessels; that is, motion of interstitial fluids. NATURE'S MODE OF SUSTAINING HEALTH. The act of transforming latent, non-vital force which exists pent-up in food, as heat is in coal, into vital energy, requires the simultaneous elimination from the system of a like amount of worn-out matter. Assimilation of nutritive materials is impossible, unless a like amount of matter be eliminated from the system. Muscular and nervous energy are dependent upon activities which cause waste. Not only is this true in a general way, but it is also true that the energy produced by the operations of the vital system has a strict relation to the wasting products--that _full_ energy is only attained by _perfected_ waste. Use, waste, and power, then, sustain definite and dependent or corresponding relations, since waste is as essential to health as is supply.