It oxidizes and renders harmless poisonous substances absorbed in the food, such as fermented food products and alcohol. The _Muscles_ oxidize the fats and sugars liberating the latent heat and energy. They partly oxidize proteins which are further broken up in the liver. The _Nerves_ oxidize food materials stored in the nerve cells, providing nervous energy. The _Lungs_ absorb oxygen and throw off carbon dioxid, watery vapor, and some organic substances. The _Kidneys_ and the _Skin_ excrete water, carbon dioxid, and nitrogenous waste. The _Blood_ carries the vital elements derived from the food to all the organs and tissues, keeping them alive and actively functioning. It also carries waste products to the skin, lungs, kidneys, and intestines for elimination. _FACTORS INFLUENCING DIGESTION_ As before stated, it is not the food eaten, but that which the body digests and assimilates, or appropriates to its needs, which counts. Many factors influence such nourishment. The principal aids are a forceful circulation, the plentiful breathing of oxygen, and free elimination. * * * * * [Sidenote: The Appetite] If one has no appetite, we have been told in the past to abstain from food until the system calls for it, or to eat but a very little of the lightest food at regular meal times. This is right, but it deals with the effect and not the cause of the lack of appetite. The chances are that this lack is due to retained waste. Whenever there is too much waste in the system, the chances are that the digestive organs will not call for more food, and when the appetite is lacking the effort should be made to see that the system is thoroughly clean. Every muscle and tissue must be relieved of the excess of waste. The correction of the lack of appetite, then, is not only abstinence from food, but brisk exercise, plenty of fresh air in the lungs, free drinking of water, and the elimination of the waste through the intestines, skin, lungs, and kidneys. One should not be led into forming the habit of irregular eating, however. The stomach forms habits and the supply of food must be regular, just as the nursing child must be fed regularly, or digestive disturbance is sure to result. Care should be taken not to eat between meals nor to eat candy or indigestible foods. The lack of appetite may be due to mental preoccupation which does not let the brain relax long enough for the physical needs to assert themselves. One should relax the brain in pleasant thought during the meal. But the chief thing to bear in mind is to create the demand for food by relieving the system of its waste, by calling for more supply to the muscles through exercise, and by giving the system plenty of oxygen through deep breathing.