arrangement which fits him to dwell in any part of the habitable globe,—yet he is subject, with regard to the actual material of his diet, in a remarkable manner, to the influence of climate, since a particular kind of aliment, which is very appropriate in one country is improper in another; thus, as we advance from the equator towards the poles, the necessity for animal food becomes greater, till, in the very north, it is the sole article of subsistence. Animal food, from containing nitrogen, is more stimulating, and, therefore, less suitable for hot climates, where, on the contrary, saccharine, mucilaginous, and starchy materials are preferred; hence, in the zone of the tropics, we find produced in abundance rice, maize, millet, sago, salep, arrowroot, potatoes, the bread-fruit, banana, and other watery, or mucilaginous fruits. Quitting this zone, we enter that which produces wheat, and here, where the temperature is lower, providence has united with the starch of this grain a peculiar principle (gluten), possessing all the properties of animal matter, and yielding nitrogen and ammonia in its decomposition[E]. Thus, by a gradual and almost insensible transition, nature furnishes to man the food which is most appropriate for him in each region. In the subtropical zone vegetable diet is still preferred, but, in chemical constitution, the favourite articles approximate animal substances. This holds also in the temperate zone, not only in respect of wheat, but also in the chesnut, which is almost the sole means of subsistence in some of the mountainous regions of France, Italy, and Spain, though, instead of the gluten of wheat, this seed contains albumen, the relation of which to animal food is even closer than that of gluten. In reviewing the geographical distribution of the cereal grains[F], we find that starch nearly pure is produced in the greatest abundance in the hottest parts of the world, particularly in rice and maize; it becomes associated in the subtropical regions with an equivalent for animal food; and in still colder regions, where wheat fails, oats and barley take its place. These, though possessed of less gluten than wheat, are, nevertheless, more heating, and, therefore, better calculated for northern latitudes. The inhabitants of Scotland and Lapland, with their oaten and barley or rye bread, are thus as thoroughly provided with the best food, as the Hindoo with his rice or Indian corn[G].

It would be impossible to enumerate the plants which furnish starch in large proportion, but a few may be given as illustrative of the above positions. The chemical analysis of those proximate principles of plants which are mere combinations of water with carbon (hydro-carbonates or hydrates of carbon) has been already given, but must here be repeated:—

These are so many mutually convertible products, of which gum may be looked upon as the basis; indeed gum is that organizable product which exists most universally in the proper juices of plants. “There are some instances in which sugar appears to be the first organic compound formed by the combination of the external elements, as when abundantly existing in the ascending sap of trees—the maple, for example. Starch may be considered as little else than gum divided into minute portions, each of which is enclosed in a membraneous cell (and containing some incidental particles, which, when starch is burnt, leave about .23 per cent. of residuum, consisting entirely of phosphates); and, in this state, it appears to answer very important ends in the vegetable economy. It is remarked by Decandolle, that, ‘while gum itself may be considered the nutrient principle of vegetation, diffused freely through the structure of the plant, and constantly in action, starch is apparently the same substance, stored up in such a manner as not to be readily soluble in the circulating fluids,’ thus forming a reservoir of nutritious matter, which is to be consumed, like the fat of animals (which it closely resembles in structure), in supporting the plant at particular periods[H].”

This view explains the fact of starch being found accumulated in amazing quantity in some plants, more particularly at certain periods of their existence, as in the cases I am now to cite. The fertility of some palm-trees is very great, and to furnish nutriment to the flowers, fruit, and seeds, an enormous supply of starch is needed; accordingly, in these we find the stem a complete storehouse of this essential principle. Thus the several palms and palm-like plants, which yield sago, such as the sagus Rumphii, cycas circinalis, C. revoluta, corypha umbraculifera, caryota urens, and phœnix farinifera—trees which are mostly confined within the tropics, at the moment when the spadices or sheaths containing the bunches of flowers are visible but not unfolded, furnish an immense portion of the food of the natives. The sagus Rumphii, which abounds in the islands of the Indian Archipelago, and though one of the humblest of the palm tribe, seldom exceeding thirty feet in height, is yet, except the gomuto, the thickest and largest, alone yields a quantity of nutritious matter far exceeding that of all other cultivated plants, inasmuch as a tree in its fifteenth year produces 600 lbs. of sago, which word, in the language of the Papuas, signifies bread, being the staple food of the islanders. To obtain it, the tree must be cut down, and the stem divided into pieces, from which the flour is beaten and washed out[I]. After being cut down, the vegetative power still remains in the root, which again forms a trunk, and this proceeds through its different stages, until it is again subjected to the axe, and made to yield its alimentary contents for the service of man. Nor is the extraordinary productiveness of a single tree the only point worthy of notice, for, being endogenous plants, devoid of branches, an unusual number of them can grow in a small space. Mr. Craufurd calculates that an English acre could contain four hundred and thirty-five sago trees, which would yield one hundred and twenty thousand five hundred pounds avoirdupois of starch, being at the rate of more than eight thousand pounds yearly. Besides the farina or meal, every tree cut down furnishes, in its terminal bud, a luxury which is as much prized as that of the areca oleracea, or