Always take advantage of any natural leverage that you can and if you must move something heavy, do not lift it at once and attempt to carry it, but lift one end and swing or shove it and then lift the other end and shove it. If you will watch expressmen at work you will notice that they roll boxes and trunks, holding them almost on end and tipping them just enough to turn them along their shortest axis. In this way the boxes carry themselves, so far as their main weight is concerned. Carrying a weight on the head or shoulders is another way of converting a pull into a push, and this is taken advantage of by peasant women in Europe, who often are seen carrying heavy weights to market in baskets perched on their heads, while they stride along arm-free. A knapsack strapped on to the shoulders is not only more convenient because it leaves the arms and hands free to swing naturally or use for other purposes, but because the weight is distributed and is carried by means of heavy muscles pushing up under the strap. A weight should be distributed over a set of muscles as evenly as possible, and this is the reason for suspending a knapsack from two shoulders instead of one, when possible. Finally, in doing any sort of lifting or pulling, if the muscles that are to be used are contracted before grasping the weight they will be able to do their work with far less effort. Try lifting a small weight like a book in two ways--first, have your hand and fingers relaxed and limp when you grasp it, and see how heavy it seems and how hard it is to contract your muscles properly while lifting it. Then drop the book and go at it again, this time anticipating its weight and contracting your hand and finger muscles before grasping it. See how easily it comes up. Try this same thing with heavier weights, and learn _always to contract the muscle before taking the load_. In carrying a weight for any distance it is well to shift it from one arm to another, always preparing the muscles by contracting them before the weight is assumed. Using the muscles so as to take advantage of their lever-like qualities in the best way, contracting them before loading, and pushing instead of pulling, go to make up what is sometimes called "getting a purchase." 4. _Supply Daily Need for Air, Sun, Water and Food_--Besides exercise and rest there are other controllable factors upon which health depends. These are air, heat and light of the sun, water and food. To grow and work properly the body needs plenty of each of these. _Air_--If you cannot work or play outdoors you can still bring out of doors in by opening your windows at frequent intervals. You will find that work goes better, and that you do not tire so easily if you make it a rule to open the windows and doors and move about the room for five minutes every hour or two. Sleep with windows open or out-of-doors. Camp and hike as often as possible. Work in the garden. Play out-of-door games.