34. Avena sativa, Linn.—The common oat.
Tribe III. Avenaceae.
History.—The oat is not mentioned in the Old Testament; but it is noticed by the ancient Greek [Hippocrates De victus ratione, lib. ii. sect. lv. p. 356, ed. Foes.; Theophrastus, Hist. Plant. lib. viii. cap. 9; Dioscorides, lib. li. cap. 116, and lib. lv. cap. 140; Galen, De Alisn. Facult. lib. i. cap. 13, p. 322, tom. vi.—Fraas (Synops. Plant. Florae Classicae, p. 303, 1845) considers that the term βρομος includes both Avena sativa and A. fatua, Linn.] and Roman [Pliny, Hist. Nat. lib. xviii. cap. 44.] writers, the former of whom called it βρομος, the latter avena.
Botany. Gen. Char.— Spikelets three, many-flowered; flowers remote; the upper one withered. Glumes two, thin, membranous, awnless. Paleae two, herbaceous; the lower one awned on the back, above the base, at the point almost bicuspidate; the upper one bicarinate, awnless; awn twisted. Stamina three. Ovarium somewhat pyriform, hairy at the point. Stigmata two, sessile, distant, villoso-plumose; with simple hairs. Scales two, smooth, usually two-cleft, large. Caryopsis long, slightly terete, internally marked by a longitudinal furrow, hairy at the point, covered by the paleae, adherent to the upper one (?) (Kunth).
Sp. Char.—Panicle equal. Spikelets two-flowered. Florets smaller than the calyx, naked at the base, alternately awned. Root fibrous, annual (Kunth).
Hab.—Cultivated in Europe.
A considerable number of varieties [For an account of the different sorts of cultivated oats, see The Agriculturist's Manual, by Peter Lawson and Son, 1836; and Supplement, 1842. Also, Loudon's Encyclopedia of Agriculture.] of this species are cultivated; these may be arranged under the two heads of white oats and the red, dun, or black oats.
The white oats have the paleae of a whitish or straw colour. To this division belong the potato oat, the Georgian oat, the Poland oat, and the Friezland or Dutch oat.
The red, dun, or black oats, are so called on account of their colour.
Besides the Avena sativa, several other species of Avena are cultivated as oats. The following are the chief:—
Avena orientalis, Kunth.—Tartarian, Hungarian, or one-seeded oat. Cultivated in Europe.
Avena brevis, Kunth.—Short oat. Germany, Austria, and Hungary. Cultivated in France and Spain.
Avena nuda, Kunth.—Naked oat. Cultivated in Europe.
Description.—Oats (caryopsides vel semina avenae cruda) are too well known to need description. As found in commerce, they are usually enclosed in the paleae or husk. When deprived of their integuments, they are called groats (semina integumentis nudata, L.; avena excorticata seu grutum): these, when crushed, are denominated Embden groats. Oatmeal (farina ex seminibus, D.) is prepared by grinding the grains. It is not so white as wheaten flour, and has a somewhat bitterish taste.
Composition.—Oats have been analyzed by Vogel [Quoted by L. Gmelin, Handb. d. Chemie, Bd. ii. S. 1345.], by Payen [Précis de Chimie Industr. 1849], and, more recently, by Messrs. Norton and Fromberg; and oatmeal by Dr. Christison [Dispensatory]. The results of Payen's analysis have been already stated (see ante, p. 106).
Four varieties of Scotch oats were analyzed by Messrs. Norton and Fromberg [Johnston's Lect. on Agricult. Chemistry, p. 886, 2d. edit. 1847.] with the following results:—
|Alkaline salts and loss||2.84||1.84||0.94||1.75|
||100.00 N||100.00 F||100.00 F||100.00 N|
Oats consists of from 22 to 28 per cent. of husks; and from 72 to 78 per cent. of grain.
The composition of the husk of the oat, according to Professor Norton, is as follows:—
||Hopeton Oat.||Potato Oat.|
|Sugar and gum||0.47||0.75|
|Gluten and coagulated albumen||1.88||1.88|
|Saline matter (ash)||6.47||6.99|
The husk of the oat, therefore, though nutritive, is less so than the bran of wheat.
1. Oat Starch, when examined by the microscope, is perceived to consist of small particles, whose normal shape is round; but which is modified by the mutual compression of the particles—some being mullar-shaped, from the mutual pressure of two particles—some being rounded at one end and dihedral at the other, from the mutual pressure of three particles—and others being polyhedric and many-angled, from the mutual pressure of many particles. The hilum is tolerably distinct in the rounded granules, but rings or laminae are not visible. The great bulk of the granules are of the medium size [The following measurements of six (including large and small) grains of oat starch were made by Mr. George Jackson:—1. 0.0010 of an English inch. 2. 0.0006. 3. 0.0004. 4. 0.0003. 5. 0.0002. 6. 0.0001.] and polyhedral, frequently presenting a pentagonal outline. Unlike most other starches, little or no variation is observed in their appearance when they are viewed by polarized light; no crosses are visible.
2. Avenin.—This is a proteine compound analogous to casein or curd of milk, and on it much of the nutritive value of oats depends. If oatmeal be washed on a sieve, and the milky liquid which runs through be left till the starch is deposited, then heated to 200° F. to coagulate the albumen, and to it, when cooled, acetic acid added, a white powder falls, which is avenin.
Chemical Characteristics.—Iodine forms, when added to the cold decoction of oats, the blue iodide of starch. Oatmeal, when mixed with water, does not form a dough as wheaten flour does; but by washing it with water on a sieve, the whole of the meal, with the exception of the coarse parts, will be washed through.
Physiological Effects.—Oatmeal is an important and valuable article of food. With the exception of maize or Indian corn, it is richer in oily or fatty matter than any other of the cultivated cereal grains; and its proportion of protein compounds exceeds that of the finest English wheaten flour. So that both with respect to its heat- and fat-making, and its flesh-and blood-making principles, it holds a high rank.
A diet of unfermented oat-bread is apt to occasion dyspepsia in those unaccustomed to its use; and it was formerly suspected of producing or aggravating chronic skin diseases, but without just grounds. Oatmeal porridge, taken at breakfast, sometimes relieves habitual constipation.
Intestinal concretions, composed of phosphate of lime, agglutinating animal matter, and the small, stiff, silky bristles seen at one end of the inner integument of the oat, are sometimes formed in those who habitually employ oats as food: forty-one specimens, collected by Dr. Monro secundus, are still in the Anatomical Museum of the University of Edinburgh. These formations are now comparatively rare, probably because the oats are more perfectly deprived of their investing membranes before being ground (Christison).
Uses.—The oat is employed dietetically and medicinally.
As a dietetical agent, it is employed in the form of oat-cake or unfermented oatbread, oatmeal porridge or stir-about, and gruel. The latter is sometimes given to infants as a substitute for the mother's milk. When there is a tendency to diarrhoea, either in adults or infants, it is advisable to substitute wheatmeal for oatmeal.
In medicine we employ gruel, prepared from groats or oatmeal, as a mild, nutritious, and, in most cases, easily-digested article of food in fevers and inflammatory affections. It is also in general use after parturition; and is the basis of caudle. In poisoning by acrid substances, it is employed as an emollient and demulcent. It is given, after the use of purgatives, to render them more efficient and less in jurious. It is frequently used, either alone or in conjunction with other agents, as a clyster. Oatmeal is used for making poultices.
Oats are also employed by distillers for the production of spirit (see Alcohol).
DECOCTUM AVENAE; Oatmeal Gruel; Water Gruel.—This is usually prepared by boiling oatmeal or groats in water for about half an hour, and then straining. Dr. Cullen [Treatise of the Materia Medica, p. 280.] directs it to be prepared by boiling an ounce of oatmeal with three quarts of water to a quart, constantly stirring; strain, and when cold decant the clear liquid from the sediment. Sugar, acids, or aromatics may be employed for flavouring.