The science of dietetics will develop rapidly in the future, and in a few years it will probably be possible to be more definite than we have been here. At present there is much unknown, especially as to how far our rules have to be modified for the particular individual. Personal idiosyncrasies have to be taken into account. Sometimes "What is one man's meat is another man's poison." On the other hand, many have mistaken ideas as to their own idiosyncrasies. For instance, many people think that nuts never agree with them, when the trouble really is that they do not masticate them properly. Many think peanuts indigestible, not realizing either the importance of mastication or the importance of avoiding over-roasting. The ordinary peanuts are over-roasted. Peanuts very slightly roasted and very thoroughly masticated seldom disagree with one. Others believe that bananas never agree with them, when the fact is they eat them too green. The banana vender usually finds that the ignorant public buys his fruit best when its color is an even yellow, and he puts aside for himself the only bananas ripe and fit to eat, namely those which are mottled with black. [Sidenote: Avoidance of Fads] Each individual must use his own intelligence and common sense, avoiding so far as he can the mistake of following a "fad" and accepting a theory without sufficient evidence; and the opposite mistake of accepting as hygienic the customs about him simply because they are customs, and thus mistaking for fads any conclusions of science which are discordant with current custom. [Sidenote: Necessity of Medical Examination] It is a good idea to consult a physician in regard to one's diet, and endeavor intelligently to follow his advice and not insist on one's own diet, selected from the standpoint of mere self-indulgence or custom. Moreover, since many, without being aware of the fact, are affected with Bright's disease, diabetes, etc., in their early stages, in which dietetic precautions are especially necessary, it is well, even for those who are apparently in good health, to be medically examined as a preliminary to a rearrangement of their diet along the best lines. CHAPTER III POISONS Section I--Constipation If the human body be likened to a steam-engine, its wastes correspond to the ashes. [Sidenote: Retention of Body Wastes] The injury which comes from the retention of the body's waste products is of the greatest importance. The intestinal contents become dangerous by being too long retained, as putrefying fecal matter contains poisons which are harmful to the body. Abnormal conditions of the intestines are largely responsible for the common headache malady, and for a generally lowered resistance, resulting in colds and even more serious ailments. Constipation is extremely prevalent, partly because our diet usually lacks bulk or other needed constituents, but partly also because we fail to eliminate regularly, thoroughly, and often.