Some eastern nations indeed, and thousands of in dividuals of every nation, live almost entirely on vege table aliment. But these, it is remarked, are seldom so robust, so active, or so brave, as men who live on a mixed diet of animal and vegetable food. Few at least in these countries of Europe can be sufficiently nourish ed by vegetable diet alone : and even those nations and individuals who are said to live exclusively on vegetables, because they do not cat the flesh of animals, generally make use of milk at least, of butter, cheese, and eggs.
A mixed diet of vegetable and animal food, is in truth that which is best suited to the nature and condition of man. The proportions in which these should be used, it is not easy to determine. But generally the quantity of vegetable should exceed that of animal food. We may observe also, that the inhabitants of wanner cli mates require less animal food than those of higher latitudes; and the sedentary of every climate less than those who labour. The sanguine and plethoric should use less animal food than those of the weak and nervous temperament. In acute, febrile, and inflammatory dis eases, animal food is universally hurtful ; but in a great variety of chronic ailments, in those especially connect ed with debility of the digestive and assimilating sys tems, it is often found to agree better than vegetable aliment.
2. Having premised these general observations on the nature of aliments, we shall now give some account of the different alimentary substances, of those more particularly, which are commonly used in Europe. We begin with those derived from the vegetable kingdom.
All the products of vegetation are not equally nutri tious. Many of the vegetable principles indeed, so far from being alimentary, are highly noxious to animal life. The wax, resins, and balsams, the astringent, bitter, and narcotic principles, are often used medicinally, but ne ver as food. And those vegetables which abound in them cannot with safety be assumed as aliments.
The alimentary principles of vegetables are gum, or mucilage, starch, gluten, jelly, fixed oil, sugar, and acids.
And the different vegetables, and parts of vegetables, are nutritious, wholesome, and digestible, according to the nature and proportion of these principles contained in them.
The lightest kind of nourishment is afforded by the mucilage, jelly, and acids of vegetables. The sugar
and fixed oils are more nutritive, but not so digestible. The starch and gluten are the most nutritive, and, to gether with mucilage, at the same time the most abun dant principles contained in those vegetables from which man derives his sustenance. Of these, the gluten ap proaches nearest to the nature of animal substances; it affords ammonia on distillation, and is susceptible of the putrefactive fermentation.
Of all the alimentary substances derived from the ve getable kingdom, the most nutritive are the seeds of the Cerealia, under which title are commonly comprehended the gramina, or cianziprous plants.
The seeds of these abound in farinaceous matter, a com pound of the most nutritive alimentary principles of ve getables. These three principles, starch, gluten, and mucilage, constitute indeed the greater part of bread corn, the most nutritious, perhaps, of all vegetable mat ters. The separation of these principles is easily effec ted by the following simple process:—Take a quantity of wheaten flour made into a paste, knead it with your hand, and wash it well and repeatedly with water. The starch is carried off with the water, and by rest subsides to the bottom of the vessel; the mucilage is at the same time separated, but remains dissolved in the water, from which it may be obtained by evaporation ; the glu ten remains in the hand, a tough, elastic, fibrous sub stance, of a greyish colour ; and when dried, semi transparent, and much resembling- glue.
Wheat flour contains by much the largest quantity of gluten ; the flour of the other nutritive grains but very little of it. It is this large proportion or gluten which gives the superiority to wheat over all the other grains, and fits it so well for the preparation of leavened or fer mented bread, the most perfect, wholesome, and nutri tious of any. It is worthy of remark, however, that wheaten bread, when used new-baked and warm from the oven, is neither so wholesome nor so digestible as when one day old. Biscuit, or unfermented bread, is hardly less nutritive than loaf bread ; hut it is, generally speaking, neither so wholesome nor so digestible. It is more apt also to induce costiveness ; yet with sonic stomachs it agrees better, from being less acescent than fermented bread.