Hygiene of the Skin.--The skin is of importance both as an organ of excretion and as a regulator of bodily temperature. The skin of the entire body should be bathed frequently so that this function of excretion may be properly performed. Pride in one's own appearance forbids a dirty skin. For those who can stand it, a cold sponge bath is best. Soap should be used daily on parts exposed to dirt. Exercise in the open air is important to all who desire a good complexion. The body should be kept at an even temperature by the use of proper underclothing. Wool, a poor conductor of heat, should be used in winter, and cotton, which allows of a free escape of heat, in summer. Cuts, Bruises, and Burns.--In case the skin is badly broken, it is necessary to prevent the entrance and growth of bacteria. This may be done by washing the wound with weak antiseptic solutions such as 3 per cent _carbolic acid_, 3 per cent _lysol_, or _peroxide of hydrogen_ (full strength). These solutions should be applied immediately. A burn or scald should be covered at once with a paste of baking soda, with olive oil, or with a mixture of limewater and linseed oil. These tend to lessen the pain by keeping out the air and reducing the inflammation. Summary of Changes in Blood within the Body.--We have already seen that red corpuscles in the lungs lose part of their load of carbon dioxide that they have taken from the tissues, replacing it with oxygen. This is accompanied by a change of color from purple (in blood which is poor in oxygen) to that of bright red (in richly oxygenated blood). Other changes take place in other parts of the body. In the walls of the food tube, especially in the small intestine, the blood receives its load of fluid food. In the muscles and other working tissues the blood gives up food and oxygen, receiving carbon dioxide and organic waste in return. In the liver, the blood gives up its sugar, and the worn-out red corpuscles which break down are removed (as they are in the spleen) from the circulation. In glands, it gives up materials used by the gland cells in their manufacture of secretions. In the kidneys, it loses water and nitrogenous wastes (_urea_). In the skin, it also loses some waste materials, salts, and water. "The Effect of Alcohol on Body Heat.--It is usually believed that 'taking a drink' when cold makes one warmer. But such is not the case. In reality alcohol lowers the temperature of the body by dilating the blood vessels of the skin. It does this by means of its influence on the nervous system. It is, therefore, a mistake to drink alcoholic beverages when one is extremely cold, because by means of this more bodily heat is allowed to escape.