From the circumstance of vegetable aliment containing _little nourishment_ and _much indigestible matter_, it naturally happens that a larger quantity of refuse remains to be thrown out of the bowels when it constitutes the chief part of the diet, than when animal or farinaceous food, which contains _much nourishment_ and _little indigestible matter_, is used. Hence, as a general rule, the bowels act more freely, or are more open, in the former than in the latter case; and hence the common saying, that milk, eggs, jellies, and meat, are _binding_. They have the appearance of being so chiefly because they are almost wholly absorbed. But as neither the stomach nor the bowels are adapted in structure for very concentrated food, such articles cannot be long used with advantage. Brown and rye bread, and fruits, are in repute for relieving a costive habit of body, and their usefulness is explicable on the same principle. They leave a large residue to be thrown out of the system, and this residue forms the natural stimulus of the bowels, and consequently excites them to freer action. This effect is probably aided also by the stimulus which the indigestible refuse imparts to the mucous glands, increasing the lubricating secretion, and giving additional facility to the propelling powers. In the preceding exposition of the structure and functions of the organs of digestion, many omissions necessarily occur, and many questions of much intrinsic interest are passed over with very little notice. But a minuter survey was incompatible with both the objects and the limits of the work. My great aim was, not so much to extend the bounds of physiology, but to turn to a useful purpose what is already known in regard to one of its most important departments, and to interest a larger class of people in its cultivation. If I have said enough to make the points of doctrine on which I have touched intelligible to the ordinary reader, and to impress him with a just sense of their practical value, I shall have accomplished the utmost I have sought to attain. PART II. THE PRINCIPLES OF DIETETICS VIEWED IN RELATION TO THE LAWS OF DIGESTION. CHAPTER I. TIMES OF EATING.