Page:The American Cyclopædia (1879) Volume I.djvu/339

ALIMENT 315 parts per thousand; and phosphate of lime exists in the bones and other solid tissues in much greater proportion. Both these substances are also ingredients of the food. Chloride of sodium is found in muscular flesh, or lean meat, in the proportion of two parts per thousand, and we are also in the habit of adding it to the food as a condiment. Breeders of sheep, cat- tle, and horses always find that a liberal sup- ply of common salt improves greatly the con- dition of the animals. Phosphate of lime exists in the muscular flesh of animals, in fish, oysters, eggs, in the cereal grains, in peas, beans, pota- toes, beets, turnips, &c., and even in most of the juicy fruits. The alkaline salts, the car- bonates of soda and potassa, are also necessary to the nourishment of the body; since the blood and most of the secretions must have an alkaline reaction, and this reaction is for the most part communicated to them by the pres- ence of the carbonates of soda and potassa. Unlike the mineral salts, however, the alkaline carbonates are not usually introduced into the body under their own form. Many of the sum- mer fruits and vegetables contain salts of soda and potassa combined with various organic acids, such as the malates, tartrates, and ci- trates of these bases. These salts are decom- posed in the interior of the body, and their vegetable acids replaced by the carbonic acid. Thus they become alkaline salts, and provide for the proper constitution of the animal flu- ids. 2. Another group of the alimentary sub- stances comprises starch and sugar. These two resemble each other in their chemical constitu- tion, being composed of carbon, hydrogen, and oxygen alone. They are further connected by the fact that starch may by various means be converted into sugar. The readiest mode of doing this is perhaps by boiling with a dilute acid. If 320 grains of starch be boiled for five hours with ' about two fluid drachms of sul- phuric acid in a pint of water, it will be found to have lost the properties of starch and ac- quired the sweet taste and other characteristic qualities of sugar. There are various other modes by which the same change may be ac- complished; and in fact in very many in- stances, if not in all, in which sugar is formed in the juices of vegetables, it has first appeared in the form of starch. Of the substances be- longing to this group, the different varieties of starch are the most abundant. Starch is found, in the form of minute rounded grains, in a vast number of vegetable productions. It is abun- dant in wheat flour, in rice, Indian corn, rye, barley, oats, potatoes, peas, and beans, and enters in smaller proportion into nearly every article of vegetable food. In the process of cooking, or heating the starch in contact with water, its grains swell up, become softened, absorb water, and at last, if the heat be suffi- ciently long continued and the water sufficiently abundant, they fuse together into a gelatinous, homogeneous mass. In this condition they are much more digestible than in the raw state, and it is in this form that starch is almost al- ways actually used as food. Sugar is also taken not only in its purified form, as an addition to other substances, but also as a natural in- gredient in the sweet juices of nearly all the fruits and most vegetables. Wheat flour con- tains 5 per cent, of sugar, milk .nearly 5 per cent., beets 9 per cent., pears over 10 per cent., and peaches and cherries from 16 to 18 per cent. Vegetable substances containing starch and sugar are always useful, and in the long run indispensable for maintaining health in the human species. A diet exclusively composed of meat and other animal substances becomes after a short time exceedingly distasteful, and an almost irresistible desire is experienced for food of a vegetable origin. This is an instinct- ive demand of the system. Even dried or pre- served vegetables will not answer the purpose indefinitely, for there is something in the fresh vegetable juices which is essential to health ; and if fresh vegetables are excluded from the food for a long time, all the symptoms of scurvy begin to manifest themselves, showing a gener- ally disordered condition of the nutritive func- tions. 3. A third group of alimentary ma- terials comprises the fats. These substances, like starch and sugar, consist of carbon, hydro- gen, and oxygen as their chemical elements, but the proportions in which the elements are combined are not analogous to those in the former group ; and the fats have other dis- tinctive characteristics also. They are both of animal and vegetable origin. They constitute the greater part of the adipose tissue or fat of animals, more than 25 per cent, of the yolk of eggs, the whole of the butter derived from cow's milk, 9 per cent, of Indian corn, 32 per cent, of olives, and in walnuts and filberts as much as 50 or even 60 per cent. Fat, in some one or more of these forms, is extremely useful and perhaps indispensable as an article of food. The fact that it constitutes over 3 per cent, of human milk, which is the first and exclusive food of the infant, shows this to be the case, at least for that age ; and the general desire which is felt by the healthy appetite for a certain pro- portion of fat is a sufficient indication of its importance. 4. The last group of alimentary materials comprises albuminoid substances. (See ALBUMEN.) They are distinguished from both the starchy and fatty substances by the fact that they all contain nitrogen ; and they are sometimes designated as the nitrogenous elements, in distinction from the others, which are non-nitrogenous. The albumen of the white of egg is one of the most important and familiar. A substance very similar in composition to albumen, namely, musculine, forms the principal mass of muscular flesh, and is the chief ingredient in lean meat used for food. Caseine is present in milk, and in a co- agulated form constitutes the principal part of cheese. Legumine is found in peas and beans, and gluten is the albuminoid ingredient of wheat flour. Altogether, an adult man usually