The principles upon which garments should be built are two: First, they should fit closely enough to the body and limbs to protect them from either injury or cold, even while free activity of every sort is allowed--you could not wrestle in a blanket or run very far in a sack. Second, they should be thick enough to protect us from cold, and yet at the same time porous enough not to interfere with the natural breathing and ventilating of the skin. A garment should be as loose as possible without interfering with our movements, and as free and as light as can be worn with reasonable warmth and protection. The less clothing you can wear and be comfortable, the better. We should particularly avoid binding or cramping the chest and the hips and waist. If clothing is too tight about the chest, it interferes both with free movement of the arms and, what is even more important, with the breathing movements of the chest. If too tight about the waist and hips, it badly cripples the lower limbs and interferes with the proper movements of the diaphragm in breathing, and with the passage of the food and the blood through the bowels. Your instincts are perfectly right that make you dislike to be squeezed or pinched or cramped in any way, or at any point, by your clothing; and if you will only follow these instincts all through your lives, you will be far healthier and happier. The Texture of Clothing. Just as for ages we have experimented with different kinds of food, so we have with different kinds of material for clothing. We have used the skins of animals; mats woven out of leaves and grasses; the feathers of birds; the skins of fishes; cloths made of wool and of cotton; and even the cocoon spun by certain caterpillars, which we call _silk_. But of all these materials, practically only two have stood the test of the ages and proved themselves the most suitable and best all-round clothing materials--wool and cotton. Woolen cloth, woven from the fleece of sheep or goats or camels or llamas or alpacas, has three great advantages, which make it _the_ outside clothing of the human species. First, it is sufficiently tough and lasting to withstand rips and tugs and ordinary wear and tear; second, it is warm--that is, it retains well the body heat; and third, it is porous, so that it will allow gases and perspiration from the surface of the body to pass through it in one direction, and air for the skin to breathe, in the other. [Illustration: RESULTS OF TIGHT CLOTHING (1) The normal thorax. (2) The thorax and organs cramped and lifted by pressure of the clothing. (From an X-ray photograph.--After Dickinson.)]