The potato is relatively deficient in flesh-forming matters, and contains the respiratory elements in exceedingly high proportions; hence it is well adapted for fattening purposes, and in this respect is equal to double its weight of the best kind of turnips. When used as food for man, it should be supplemented by some more fatty or nitrogenous substance—such, for example, as flesh, oatmeal, or peas. Buttermilk, a fluid which is rich in nitrogen, is an excellent supplement to potatoes, and compensates to a great extent for the deficiency of those tubers in muscle-forming matters. If, then, the potato is destined to retain its place as the "national esculent" of the Irish, I trust their national beverage may be—so far at least as the masses of the people are concerned—buttermilk, and not whiskey.
Potatoes so far diseased as to be unsuited for use as food for man, may be given with advantage to stock. They may be used either in a raw or uncooked state, but the latter is the preferable form. Sheep do not like them at first, but on being deprived of turnips they acquire a taste for them; on a daily allowance, composed of 1 lb. of oil-cake or corn, and an unlimited quantity of potatoes, they fatten rapidly. Cattle thrive well on a diet composed of equal parts of turnips and diseased potatoes, and do not require oil-cake. The evening feed of horses may advantageously be composed of potatoes and turnips. If raw, the potatoes should be given in a very limited quantity—four or five pounds; in the cooked state, however, they may be given in abundance, but the animals should not, after their meal, be permitted to drink water for some hours. As a feeding substance, diseased potatoes, unless they be very much injured, are equal to twice their weight of white turnips; it is certain that they do not injure the health or impair the condition of the animals which feed upon them.
SECTION VI.
SEEDS.
In seeds the elements of nutrition exist not only in the most highly elaborated, but also in the most concentrated state; hence their nutritive value is greater than that of any other class of food substances.
Wheat Grain is the most valuable of seeds, as it contains, in admirably adjusted proportions, the bone, the fat, and the muscle-forming principles. In the form of bread, it has been, not inaptly, termed the "staff of life," for no other grain is so well adapted, per se, for the sustenance of man; and many millions of human beings subsist almost exclusively on it. The lower animals are in general fed upon the grain of oats, of barley, and of the leguminous plants, and the use of wheat is almost completely restricted to the human family.
Wheat grain, by the processes of grinding and sifting, is resolvable into two distinct parts—bran and flour. In twenty-four analyses made by Boussingault, the proportion of the bran was from 13·2 to 38·5 per cent. and that of the flour from 61·5 to 86·8 per cent. The floury part is of very complex structure; it includes starch, gluten, albumen, oil, gum, gummo-gelatinous matter, sugar,[!--33--][33] and various saline matters. The gluten and albumen constitute the nitrogenous, or flesh-forming principles of flour, and make up from 16 to 20 per cent. of that substance; the non-nitrogenous, or fat-forming elements, such as starch and gum, form from 74 to 82 per cent. According to Payen, the proportion of gluten diminishes towards the centre of the seed, from which it follows that the part of the grain nearest the husk is the most nutritious—so far at least as muscle-making is concerned. The desire on the part of the public for very white bread has led to the fine dressing of Wheat-grain, and consequently to the separation from that substance of a very large proportion of one of its most nutritious constituents. Crude gluten may be obtained by kneading the dough of flour in a muslin bag under a small current of water; the starch, or fecula, and the gum, are carried away by the water, and the gluten in an impure form remains as an elastic viscous substance, which on drying becomes hard and brittle. It is to the gluten of flour that its property of panification, or bread-making, is due. On the addition of a ferment, a portion of the starch is converted into sugar and carbonic acid gas, and the latter causes the gluten to expand into the little cells, or vesicles, which confer upon baked bread its light, spongy texture.
| ANALYSES OF WHEAT. | ||||
| 1. | 2. | 3. | 4. | |
|---|---|---|---|---|
| Whole Grain. | Flour. | Bran. | Husk. | |
| Water | 15·00 | 14·0 | 13 | 13·9 |
| Flesh-formers | 12·00 | 11·0 | 14 | 14·9 |
| Fat-formers | 68·50 | 73·5 | 55 | 55·8 |
| Woody fibre | 2·75 | 0·7 | 12 | 9·7 |
| Mineral matter | 1·75 | 0·8 | 6 | 5·7 |
| ——— | ——— | ——— | ——— | |
| 100·00 | 100·0 | 100 | 100·0 | |
| Nos. 1, 2, and 3.—The mean results of a great number of analyses. | ||||
| No. 4.—By Millon. | ||||
Over-ripening of Grain.—The final act of vegetation is the production of seed, after the performance of which function many plants, having accomplished their destined purpose, perish. The grasses (which include the cereals) are annuals, or plants which have but a year's existence, consequently their development ceases so soon as they have produced their seed. When wheat, oats, and the other cereals, attain to this final point in their growth, the circulation of their sap ceases, their color changes from green to yellow, and they undergo certain changes which destroy their power of assimilating mineral matter, and consequently render them no longer capable of increasing their weight.