It would be easy to fill many pages with disquisitions about the preference due to individual articles of food, were such the purpose which I had in view. But books devoted to this branch of the subject abound, and are already in general circulation; and as I have nothing new to add to what is contained in them and to the general view given in a preceding chapter, it would be making a needless demand on the patience of the reader merely to repeat what is to be found in so many other works. My object is the exposition of PRACTICAL PRINCIPLES rather than of minute details; and my great aim is to enable every intelligent person to understand, not only what digestion, is, but the laws by which it is regulated, so that he may know at once WHY it is for his advantage to adhere to one course of conduct in preference to another in regard to it--WHY, in different situations, diet requires to be modified in order to adapt it more effectually to the varying wants of the system--and, lastly, the circumstances or rules by which such modifications ought to be determined. If I have succeeded in the attempt to explain any of all of these principles sufficiently to render them susceptible of a practical application by the reader, not only I will be greatly pleased, but the advantage to him will speedily convince him that I have acted judiciously in forsaking the beaten path, and drawing his attention to truths of still greater importance to his welfare than those which are most commonly treated of under the title of Dietetics. CHAPTER IV. CONDITIONS TO BE OBSERVED BEFORE AND AFTER EATING. General laws of organic activity apply to the stomach as well as to other parts--Increased flow of blood towards the stomach during digestion--Hence less circulating in other organs--And consequently less aptitude for exertion in them--Bodily rest and mental tranquillity essential to sound digestion--Rest always attended to before feeding horses--Hence also a natural aversion to exertion immediately after eating--Mischief done by hurrying away to business after meals--Severe thinking hurtful at that time--Playful cheerfulness after dinner conducive to digestion--The mind often the cause of indigestion--Its mode of operation explained--Also influences nutrition--Illustration from Shakspeare.--Importance of attending to this condition of health enforced. Having now discussed the principles by which the number, quantity, and quality of our meals ought to be regulated, we have next to consider the conditions required for the healthy performance of digestion after the aliment has reached the stomach, and to deduce from them such practical rules as shall tend to facilitate the accomplishment of the process.