In recent years there has been a revival of the theory of prolonged mastication of a limited amount of food. This theory is sound in so far as it tends to overcome the bolting of food and over-eating, but there is a belief among our practitioners that there is little basis in science or experience for the extremes of this character. HYGIENIC CURE-ALLS Among recent fads is the so-called buttermilk or sour milk diet as advocated by Metchnikoff. The original theory was interesting and was, in part, that the bacteria derived from soured milk would drive out of the intestinal canal all the harmful germs. Quite possibly there may be something in the theory, especially if large quantities of milk are taken with the lactic acid bacilli, but the beneficial effect of this change of bacteria is not convincingly of great consequence. FRESH AIR It is now generally known that an abundant supply of moving, pure, fresh air is the proper and simple solution of the problem of the hygiene of the air. Oxygen is the element of the air which sustains life. We inhale about seven pounds per day, two pounds of which are absorbed by the body. The air becomes dangerous, or infected, when the oxygen in the air is decreased to only 11 or 12 per cent., and when the oxygen reaches 7 per cent. death occurs from asphyxiation. The human body requires about three thousand cubic feet per hour, and the great problem of ventilation is to give this amount of pure air, moving, and with the proper amount of moisture. It is a common belief that with each breath we take we are filling our lungs with fresh air. This is not the case, for we never do get our lungs filled with fresh air. What really happens is that we ventilate a long tube which has no intercommunication whatever with the blood. Most of the time our lungs are filled with impure air, and we simply exchange a part of it for fresh air. THE VALUE OF DEEP BREATHING Deep breathing is undoubtedly extremely beneficial. Most of us, due largely to the fact that Nature leaves a considerable margin of safety, are able to carry on our ordinary activities without the requisite ventilation of the lungs, especially if we do not exercise. This, however, is injurious to the lungs, for it allows the blood to stagnate in them. Exercise is Nature's method of compelling ventilation in the lung area. Deep breathing may be used as a substitute, but the other beneficial effects of exercise are lost. The skin and the various glands connected with it form a complex organism, the functions of which play a very important part in the work which the body has to do. The skin aids the lungs in their work of respiration; and, like the lungs, it throws off water and carbon dioxide and absorbs oxygen. The respiratory work of the skin, however, is only a minute fraction of that which the lungs do.