Generally, however, fruits do not greatly abound in nutritive farina. The nourishment afforded by them is of the lighter kind, and derived from the mu ilage and sugar which they contain. Together with these principles and water, many of them contain also the different vegetable acids, the malie, citric, tar trous, and oxalic. It is this combination Nvhi,ch renders them so agreeable to the taste, and so relished by man.
From this combination of principles too, may be deri ved the advantages and disadvantages they possess as aliments. They are nourishing in proportion to the mucilage, jelly, and sugar, which they contain ; cooling, aperient, nd antiseptic, in proportion as they are wa tery..nd acidulous. They are not of themselves capa ble of long supporting the strength and renewing the waste of the system ; but, conjoined with other more nutritious aliment, ripe fruits are in their season safe, useful, and often highly beneficial adjuvants to our diet. Thev obviate and correct the stimulant and septic ef fects of animal food, open the body, and cool and re fresh the system. Hence they are found so eminently useful in febrile, inflammatory, and scorbutic affections. Indeed in the sea scurvy, a disease arising from the too exclusive use of a stimulating animalized diet, the subacid fruits are sovereign remedies. By the same properties, however, they are hurtful in cases of gra vel, stone, and diabetis ; and generally in all those dis eases arising from, or connected with, an inperfect assimilation and consequent acidity of the pi imm Intemperately eaten, fruits have in all constitutions, and particularly in the nervous, dyspeptic, and hysteric, pro duced great disoi der of the stomach and bowels, cholic, diarrhoea, and cholera. Upon the whole, as a part of our daily diet, fruits are safe and useful : but, excepting un der particular circumstances, they ought not to form the whole of any one meal, and should never be indulged in to satiety.
The pulpy fruits, such as the fig and apple tribe, are more nutritive than the more watery acidulous fruits, as the orange, grape, and berry. The former too, when conserved, boiled, or baked, afford a light and wholesome nourishment. The subacid fruits, as goose berries and currants, are advantageously made into tarts, jellies, Cc. or otherwise conserved with sugar. The
nourishment derived from them is not very great ; but they are wholesome, antiseptic, and cooling. The skins and husks, of fruits, and the hard seeds of berries, arc nearly, or altogether indigestible. It is needless to be more particular ; after what has been said, it will be sufficient to subjoin a list of the principal esculent Fruits, to which our general observations may with little variation be applied : We have now reviewed the principal alimentary sub stances derived from the vegetable kingdom. Upon the whole, it appears, that these are nutritive nearly in proportion to the quantity of Farinaceous matter contained in them. For the most nutritive, and at the same time the most abounding in farina, are the seeds of the gramina and leguminosm, after which may be ranged the oleo-farinaceous seeds, the alimen tary roots, herbs, and fruits. The farina of wheat. we have seen, is a compound of starch, mucilage, and gluten. But as starch and mucilage constitute the farinaceous matter of most other grains and nutritive roots, these must be regarded as the chief alimentary principles of vegetables. The other principles are less constant. Of these, the oil is the most nourishing ; sugar too is alimentary ; the acids hold the lowest rank.
3. Animal substances, as well as the vegetable, are easily resolved into a certain number of proximate prin ciples. Those which are alimentary, are gelatine, albu men, fibrine, and oil or fat.
Gelatine, or animal jelly, is the well known colour less, transparent, tremulous substance, extracted from calves' feet and hartshorn, and so elegantly prepared for our tables. Glue and isinglass are specimens of dried gelatine. This principle is distinguished by its solu bility in cold water, and by the gelatinous form which it assumes when evaporated by heat, and allowed to cool. Gelatine exists in almost every animal substance ; in particular, it abounds in the skin, the tendons, and bones, from which, in consequence of its solubility, in hot water, it is easily extracted by boiling. Gelatine is less ani malized than the other principles, that is, it contains less nitrogen, and yields consequently less ammonia when destructively analized.