The general rule, then, is, that three hours be given to the stomach for labor, and two for rest; and in obedience to this, five hours, at least, ought to elapse between every two regular meals. In cases where exercise produces a flow of perspiration, more food is needed to supply the loss; and strong laboring men may safely eat as often as they feel the want of food. So, young and healthy children, who gambol and exercise much, and whose bodies grow fast, may have a more frequent supply of food. But, as a general rule, meals should be five hours apart, and eating between meals avoided. There is nothing more unsafe, and wearing to the constitution, than a habit of eating at any time, merely to gratify the palate. When a tempting article is presented, every person should exercise sufficient self-denial, to wait till the proper time for eating arrives. Children, as well as grown persons, are often injured, by eating between their regular meals, thus weakening the stomach, by not affording it any time for rest. In deciding as to _quantity_ of food, there is one great difficulty to be met by a large portion of the community. It has been shown, that the exercise of every part of the body is indispensable to its health and perfection. The bones, the muscles, the nerves, the organs of digestion and respiration, and the skin, all demand exercise, in order properly to perform their functions. When the muscles of the body are called into action, all the blood-vessels entwined among them are frequently compressed. As the arteries are so contrived, that the blood cannot run back, this compression hastens it forward, through the veins, towards that organ. The heart is immediately put in quicker motion, to send it into the lungs; and they, also, are thus stimulated to more rapid action, which is the cause of that panting which active exercise always occasions. The blood thus courses with greater celerity through the body, and sooner loses its nourishing properties. Then the stomach issues its mandate of hunger, and a new supply of food must be furnished. Thus it appears, as a general rule, that the quantity of food, actually needed by the body, depends on the amount of muscular exercise taken. A laboring man, in the open fields, probably throws off from his skin ten times the amount of perspirable matter, which is evolved from the skin of a person of sedentary pursuits. In consequence of this, he demands a far greater amount of food and drink.