_Fourth, Thoroughly masticate all food_: Horace Fletcher has written a very enthusiastic book on this subject. Enthusiasm is apt to lead one astray, and even if thorough mastication will not do all that Mr. Fletcher believed, it is very important, and we owe Mr. Fletcher thanks for calling our attention to the subject forcibly. Thorough mastication partially checks overeating. Our foods have to be finely divided and subdivided or they can not be thoroughly acted upon by the digestive juices. The stomach is well muscled and churns the food about, helping to comminute it, but it can not take the place of the teeth. All foods should be thoroughly masticated. While the mastication is going on the saliva becomes mixed with the food. In the saliva is the ptyalin, which begins to digest the starch. Starch that is well masticated is not so liable to ferment as that which gets scant attention in the mouth. Starches and nuts need the most thorough mastication. If thorough mastication were the rule, meat gluttons would be fewer, for when flesh is well chewed large quantities cause nausea. Milk digests best when it is rolled around in the mouth long enough to be mixed with saliva. To treat milk as a drink is a mistake, for it is a very nourishing food. All kinds of nuts must be well masticated. If they are not they can not be well digested, for the digestive organs are unable to break down big pieces of the hard nut meats. The succulent vegetables contain considerable starch. If mastication is slighted they often ferment enough to produce considerable gas. Fruits are generally eaten too rapidly, and therefore often produce bad results. Even green fruits can be eaten with impunity if they are very thoroughly masticated. Those who are fond enough of liquors to take an excess should sip their alcoholic beverages very slowly, tasting every drop before swallowing. This would decrease their consumption of liquor greatly. Even water should not be gulped down. It should be taken rather slowly, especially on hot days. During hot weather many drink too much water. This tendency can usually be overcome by avoiding iced water and by drinking slowly. These four rules should be a part of your vital knowledge. If you forget everything else in this book, please remember them and try to put them into practice: _Eat only when hungry. During acute illness fast. Be moderate in your eating. Thoroughly masticate all food._ CHAPTER IX. CLASSIFICATION OF FOODS. Food is anything which, when taken into the body under proper conditions, is broken down and taken into the blood and utilized for building, repairing or the production of heat or energy. There are various forms of foods, which can be divided into two classes: First, nitrogenous foods or proteins. Second, carbonaceous, foods, under which caption come the sugars, starches and fats. Salts and water are not usually classified as foods, though they should be, for life is impossible without either.