tubers, seed-vessels, stalks, and leaves. The most important of the proximate principles are gluten, farina, mucilage, oil, and sugar. In all those nations

6 Haller attempts to reduce all nutritious substances to one principle, jelly; El. Phys. xix. 3. 2; Cullen thinks, that the matter of nutrition is, in all cases, either "oily, saccharine, or what seems to be a combination of the two." Physiol. § 211. In his treatise on the Mat. Med. v. i. pt. 1. ch. 1. p. 218. et seq. he endeavours to show that acid, sugar, and oil, contain all the principles which contribute to compose the animal fluids. An account of the various articles employed in diet, is contained in the second chapter, p. 240. et seq. Fordyce also makes an unfortunate attempt at generalization, in reducing all the nutritious matter to mucilage; Treatise on Digest. p. 84; but as he admits of a farinaceous mucilage, a saccharine mucilage, &c. it is rather a verbal, than an actual inaccuracy; p. 91..107. In like manner he says that all the animal solids consist of mucilage and water; p. 86. The proximate vegetable principles mentioned in the text, as serving for nutrition, are those which are generally employed by the human species; it appears, however, that certain species of animals can extract nourishment from parts which are not capable of being digested by the organs of man; the beaver, for example, can digest the bark and wood of trees; Blumenbach's Comp. Anat. p. 139. Richerand attempts to show that the alimentary principle is, in all cases, either gummy, mucilaginous, or saccharine; El. Phys. § 3. p. 82. Dumas is disposed to regard mucus as the "principe eminemment nutritif," because, as he says, it forms the basis of our organs and of our humours; Physiol. t. i. p. 187; we may conclude, therefore, that by the term mucus he means albumen. Sir H. Davy, in the third of his lectures on agricultural chemistry, gives a concise view of the proximate principles of the vegetables that are ordinarily employed in diet; p. 73. et seq. M. Magendie classes all alimentary substances under the heads of farinaceous, mucilaginous, saccharine, acidulous, oily, caseous, gelatinous, albuminous, and fibrinous; Physiol. t. ii. p. 3, 4.

which have arrived at any great degree of civilization, the main bulk of the vegetable food is derived from seeds of various kinds, and particularly from some of the cerealea; of these wheat has always been held in the highest estimation. In some countries rice composes a large proportion of the food of the inhabitants, and in many of the warmer climates maize is largely employed.

Gluten has been considered as the best adapted for the purposes of nutrition of any of the vegetable principles, both in consequence of its being of easy digestion, and of its containing, in proportion to its bulk, the greatest quantity of nutriment. This circumstance depends upon its being the substance, the elements of which the most nearly resemble those of the animal kingdom, hence termed the most animalized of any of the vegetable principles, and this chiefly in consequence of the large quantity of nitrogen which it contains. It exists in the greatest proportion in wheat, while it is found in small quantity only in the other kinds of seeds, or in the parts of plants generally.7

7 We have a detail of the chemical relations of gluten, in Thomson's System, t. iv. sect. 19. It has been resolved by Sig. Taddie, into two proximate principles, which he has named gliadine and zimome; see Ann. Phil. v. xv. p. 390, 1. and v. xvi. p. 88, 9. An account of the original observations of Beccaria will be found in Bonon. Acad. Com. t. i. p. 123. et seq. Vogel examined two species of wheat which are cultivated in Bavaria, the triticum hibernum, and spelta; the former was found to contain 24 per cent. the latter 22 per cent. of gluten; Journ. Pharm. t. iii. p. 212.

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Next to gluten, in point of importance as an article of nutrition, comes the farina; this is also found copiously in wheat and the other grains, and it likewise forms a considerable proportion of the nutritive parts of the various kinds of pulse and of tubers." The nutrition of leaves, stalks, and of seed-vessels, and the green parts of plants, resides in the mucilage which they contain, although, in most cases, this is united with a portion of saccharine matter, which materially contributes to their nutritive powers. Most fruits contain a basis of mucilage or farina, which is combined either with sugar or with oil. In the pulpy fruits, with the exception of the olive, the former chiefly prevails; they generally also contain a quantity of acid, in addition to their other ingredients, but it may be doubted whether the acid serves directly for the purposes of nutrition, or whether it should not be rather considered as indirectly promoting digestion, by its effect upon the stomach or the palate. The principal ingredients of the chesnut, which, in many countries, composes a large share of the diet of the inhabitants, are farina and sugar, while many of the nuts are composed of a

8 For an account of the chemical relations of farina, see Thomson's Chem. v. iv. sect. 17; Henry's Elem. v. ii. sect. 9; and Thenard, Chim. t. iii. p. 211..226. According to Braconnot, Ann. Chim. et Phys. t. iv. p. 383. rice contains 85 per cent. of farina; Vogel, Journ. Pharm. t. iii. p. 214. conceives the farina in rice to be as much as 96 per cent.; see also the analysis of rice by Vauquelin, ibid. p. 320..

basis of albumen, united to a quantity of sugar and

oil.9

Sugar enters into the composition of many vegetable substances that are employed in diet, and although it is generally regarded rather as a condiment, than as a direct source of nourishment, yet it has been supposed to be the most nutritive of all the vegetable principles. Nearly the whole of the sugar that is consumed in Europe is produced from the sugar cane, the juice of which contains it in large quantity and in a state of considerable purity. Sugar is also procured from the root of the beet in considerable quantity, and in some parts of America from the sugar maple.' Oil, either animal or vegetable, is commonly employed, more or less, in diet, and is likewise conceived to be highly nutritive; in the warmer climates vegetable oil is principally used, whereas in the colder regions animal oil is employed, as procured from milk, in the form of butter,

9. See Boullay and Vogel on the analysis of the almond; Journ. de Pharm. v. iii. p. 837, 344.

1 Dr. Thomson gives a list of the plants which contain sugar; Chem. v. iv. p. 31. There was a good deal of discussion among the older writers, respecting the nutritive properties of sugar; Lewis, Mat. Med. v. ii. p. 289, observes that in consequence of its property of uniting oily and watery bodies, it has been supposed by some to enable the unctuous part of the food to unite with the animal juices, while others have conceived, that, from the same cause, it will prevent the separation of the oily part of the food, and thus prevent it from contributing to nutrition; the author properly remarks, that experience has not shown that sugar can produce either of these effects.

There are two points of view in which the articles of diet may be contemplated, either as they are nutritive, or as they are digestible; the former respects their capacity of affording the elements of chyme; the latter, the power which the stomach has of causing them to undergo the necessary change. Between these there is an essential difference, and they do not, by any means, bear an exact proportion to each other. There are many substances, which appear to contain the largest proportion of the elements which constitute chyme, but which are by no means easily digested, and which are rendered more so by being mixed with other substances which are less nutritive.2

2 This distinction is very clearly pointed out by M. Chaussier, in the art. "Digestion," Dict. de Scien. Med. an article which, although very diffusely written, contains much useful information. In the introduction to Spallanzani's work by Sennebier, we have a detail of a set of important experiments by Goss on the comparative digestibility of different kinds of alimentary substances. He had acquired the habit of swallowing air, which acted upon the stomach as an emetic, and thus enabled him to bring up its contents at pleasure, and to examine their state in the different stages of the digestive process; p. cxxxi..CXL. The experiments that have been adduced by M. Magendie, to prove that a proportion of azote is necessary for the support of animals, in which it was found that animals cannot live for any length of time upon pure sugar, oil, or gum, Physiol. t. ii p. 390. and Ann. de Chim. et Phys. t. iii. p. 66. et seq., I conceive prove no more than that the stomach is not capable of digesting these substances without some addition. Haller observes that certain animals are destroyed by the use of sugar, although to others it proves highly nutritive and salutary; El. Phys. xix. 3. 12. In Stark's experiments we have many examples of the indigestible nature of a diet composed of a single article, which