Objections have been stated to several of the repetitions which occur in the following pages. The only apology I have to offer for them is, that I committed them deliberately, because they seemed to me necessary to ensure clearness, and because the intimate manner in which the different functions are connected with each other, sometimes made it impossible to explain one without again referring to the rest. My prime objects being to render the meaning unequivocally plain, and impress the subject deeply upon the reader’s mind, I thought it better to risk in this way the occasional repetition of an important truth, than to leave it in danger of being vaguely apprehended, or its true value unperceived. For these reasons, it is hoped that the fault--if such it is--will be leniently overlooked. Those who wish to study more fully the subject of Dietetics, will find much useful information in Dr Hodgkin’s “Lectures on the Means of Promoting and Preserving Health;” Professor Dunglison “On the Influence of Atmosphere and Locality, Change of Air and Climate, Seasons, Food, Clothing, Bathing, Exercise, Sleep, Corporeal and Intellectual Pursuits, &c. &c. &c. on Human Health;” Dr Paris “On Diet;” and Dr Kilgour’s “Lectures on the Ordinary Agents of Life, as applicable to Therapeutics and Hygiène.” CHAPTER I. GENERAL VIEW OF THE OBJECTS AND LAWS OF NUTRITION. Waste or loss of substance always attendant on action.--In the vegetable and animal kingdoms waste is greater than in the physical.--Living bodies are distinguished by possessing the power of repairing waste.--Vegetables, being rooted in one place, are always in connexion with their food.--Animals, being obliged to wander, receive their food at intervals into a stomach.--Nutrition most active when growth and waste are greatest.--In vegetables the same causes which increase these processes also stimulate nutrition.--But animals require a monitor to warn then when food is needed.--The sense of Appetite answers this purpose.--The possession of a stomach implies a sense of Appetite to regulate the supplies of food. Throughout every department of Nature waste is the invariable result of action. Even the minutest change in the relative position of inanimate objects cannot be effected without some loss of substance. So well is this understood, that it is an important aim in mechanics to discover the best means of reducing to the lowest possible degree the waste consequent upon motion. Entirely to prevent it is admitted to be beyond the power of man; for, however nicely parts may be adjusted to each other, however hard and durable their materials, and however smoothly motion may go on, still in the course of time loss of substance becomes evident, and repair and renewal become indispensable to the continuance of the action.