And again—
Feast-won, fast-lost, one cloud of winter showers.
These flies are couched.
While climate points out the most suitable articles of food, it exercises a singular influence over their qualities and properties, more especially in vegetable substances. We find plants which are poisonous in some countries, edible and wholesome in others. Next to climate, culture and soil modify plants to a singular degree: flowers which yield a powerful perfume in some latitudes, are inodorous in others; and, according to climate, their aroma is pleasant or distressing. A striking proof of this fact can be adduced from the well-known effects of perfumes in Rome; where the inhabitants, especially females, cannot support the scent even of the rose, which has been known to produce syncope, illustrating the poet’s line to
Die of a rose in aromatic pain.
This variety in the action of vegetable substances is more particularly observable in such as are considered medicinal. Opium, narcotics, and various drugs, are more powerful in warm climates than in northern regions. The Italian physicians express astonishment at the comparatively large doses prescribed by our practitioners.
Cultivation brings forth singular intermediate productions; and by its magic power we have seen the coriaceous and bitter almond transformed into the luscious peach, the sloe converted into the delicious plum, and the common crab transformed into the golden pippin. The same facts are observed in vegetables; the celery sprung from the nauseous and bitter apium graveolens, and the colewort, is metamorphosed into the cabbage and the cauliflower. All cruciform plants degenerate within the tropics, but acquire increased energies in cold countries.
Recent experiments in Germany have demonstrated that in times of scarcity, the wood of several trees may be converted into a nutritious substance. The fibres of the beech, birch, lime, poplar, fir, and various other trees, when dried, ground, and sifted into an impalpable powder, constitute a very palatable article of food. If cold water be poured on this ligneous flour, enclosed in a linen bag, it becomes milky, and considerable pressure and kneading is required to express the amylaceous or starchy part of it. Professor Von Buch, in his travels through Norway and Lapland, has fully described the Norwegian barke bröd. We find the savages scattered along the coast of the great austral continent mixing up a paste of the bark of the gum-tree with the ants and the other insects, with their larvæ, which they find in it. Ground dried fish and fish-bones have from time immemorial been converted into bread; Arrianus tells us that Nearchus found several nations on the shores of the Red Sea living upon a bread of this description.
It is thus evident that all substances from the animal and vegetable kingdom appear to afford more or less nutriment, provided that they contain no elements unlike the animal matter of the being they are intended to nourish. All others are either medicinal or poisonous. Food may be considered nourishing in the ratio of its easy digestion or solution. Magendie attributes the nutritious principle to the greater or lesser proportion of nitrogen or azote. According to his view of the subject, the substances that contain little or no nitrogen are the saccharine and acid fruits, oils, fats, butter, mucilaginous vegetables, refined sugar, starch, gum, vegetable mucus, and vegetable gelatin. The different kinds of corn, rice and potatoes, are elements of the same kind. The azotical aliments, on the contrary, are vegetable albumen, gluten, and those principles which are met with in the seeds, stems and leaves of grasses and herbs, the seeds of leguminous plants, such as peas and beans, and most animal substances, with the exception of fat.
To this doctrine, it was objected, that animals who feed upon substances containing little nitrogen, and the field negroes, who consume large quantities of sugar, might be adduced as an exception. Magendie replies, that almost all the vegetables consumed by man and animals contain more or less nitrogen—that this element enters in large quantity in the composition of impure sugar—and lastly, that the nations whose principal food consists in rice, maize, or potatoes, consume at the same time milk and cheese.
To support his theory, this physiologist had recourse to various curious experiments on dogs, whom he fed with substances which contained no nitrogen. During the first seven or eight days, the animals were brisk and active, and took their food and drink as usual. In the course of the second week they began to get thin, although their appetite continued good, and they took daily between six and eight ounces of sugar. The emaciation increased during the third week; they became feeble, lost their appetite and activity, and at the same time ulcers appeared in the cornea of their eyes. The animals still continued to eat three or four ounces of sugar daily, but, nevertheless, became at length so feeble as to be incapable of motion, and died on a day varying from the 31st to the 34th: and it must be recollected that dogs will live the same length of time without any food.