Page:The American Cyclopædia (1879) Volume VI.djvu/109

 DIETETICS 101 the Arabic grammar entitled Alfiyah (1854), Diepropadeutischen Studien der Araber (1851), Chrestomathie ottomane (1865), and other works. DIETETICS. For his complete nutrition man must have in his food the albuminoid materials of which his tissues are mainly composed, the iron and the salts contained in those tissues and in the blood, and fatty matter, or some substance which can readily be converted into fat, which enters into the composition of his body, and which serves to maintain the animal heat. (See ABSTINENCE, ALIMENT, ANIMAL HEAT, and DIGESTION.) But food must not only contain all the principles necessary to nutrition, it must likewise be digestible and assimilable ; it must be capable of being disin- tegrated and dissolved in the alimentary canal, so that it may be absorbed, and finally con- verted into blood from which the waste of the tissues may be supplied. An article may be highly nutritious, yet exceedingly indigestible ; or it may be -easily digestible, and afford little nutriment. While certain articles and classes of articles are in general more digestible, there is no rule of invariable application. There are differences in kind as well as in degree in the digestive powers of different individuals ; and what will offend the stomach of one man, an- other will digest with ease. But aside from individual peculiarities, there are more general causes of difference. 1. Habit has great in- fluence. What men have been accustomed to, they digest with greater facility. An Ameri- can or Englishman visiting the continent of Europe is frequently attacked with diarrhoaa, from an unaccustomed diet, which is in it- self equally wholesome with his own. During the revolutionary war numbers of the troops from the southern states while on duty at the north became ill, and their health was only restored by an allowance of fat ba- con. The ill-fed Irishman, on enlisting into the British army, frequently is affected with what is termed a " meat fever ; " his new diet is so much superior to what he was accustomed to, that his organs do not readily adapt themselves to the change. 2. Circumstances have a great influence on the digestibility of food. A diet suited to Labra- dor would be oppressive and injurious in the West Indies. The season, amount of clothing, exposure, and exercise have an influence on the digestive capacity as well as on the require- ments of the system. 3. The digestibility of food is much influenced by our liking for it ; within certain limits, what we are fond of agrees with us, and what we dislike is not apt to di- gest well. The high flavor which excites the appetite of the epicure provokes nausea in a less cultivated stomach. Still, despite the va- rious sources of diversity, some articles are for the majority of men of comparatively easy di- gestion, while others are assimilated with greater difficulty. Food is commonly classed as animal or vegetable. Animal food may be subdivided into the flesh of mammals, birds, fishes, reptiles, crustaceans, and mollusks. The flesh of the mammals, and indeed of the birds and fishes used for food, differs very little in chemical composition. The fibrine, albu- men, and gelatine of which chiefly they are made up, may be considered as chemically identical, from whatever animal they may be derived. The fats differ in the relative propor- tions, and sometimes in the character, of the fatty acids which enter into their composition ; the saline matters, varying in their propor- tions, are mainly of the same character; while the immense variety of flavors by which they are distinguished depend upon principles ex- isting in exceedingly minute proportions, and for the most part soluble in water. The differ- ence in meats arises from the varying propor- tions of fibrine, gelatine, and fat, and from variations in mechanical texture ; and to these circumstances is due their difference in diges- tibility. Whatever renders the animal fibre harder, makes the. meat less digestible ; what- ever renders it more delicate and tender, more easily separated and disintegrated, makes it more easily soluble in the juices of the stom- ach. Provided an animal has reached ma- turity, the tenderness of its meat is increased by youth, by its not having been worked, by its being in good condition, the muscular fibres interpenetrated and separated by minute pro- portions of fatty tissue. Keeping tends very much to improve the tenderness of meat. Few animals are fit to be eaten the day they are killed ; but when kept, long before the slight- est taint can be detected, a change takes place that renders the fibres more easily separated and disintegrated, more readily broken down and comminuted during mastication, and more quickly reduced and assimilated by the stom- ach. Of the different meats, venison that has been well kept is, in its season, perhaps the most tender and digestible. Dr. Beaumont found that in St. Martin a meal of broiled veni- son steak was completely digested and removed from the stomach in an hour and a half, a shorter time than was required by any other meat. Wether mutton of a proper age, that has hung for a sufficient length of time, is scarcely inferior in digestibility to venison. Beef ranks next to mutton. Lamb and veal are less digestible than mutton or beef, and veal is less readily digested than lamb. Of all the meats in ordinary use, pork is most refrac- tory to the gastric juices ; and, contrary to what holds with regard to beef and mutton, the sucking pig is more digestible than pork. The fat of meats generally, and all varieties of fatty matters, are difficult of assimilation ; they are particularly offensive to weak stomachs, sometimes appearing to form an oily pellicle^ which, floating on the partially chymified mass; becomes rancid and occasions distressing heart- burn and nausea, or causes eructations of acrid matter which leave a peculiarly disagreeable taste upon the palate. The mode of dressing