Physicians formerly recommended highly a diet-drink made from Oats, about which Hoffman wrote a treatise at the end of the seventeenth century; and Johannis de St. Catherine, who introduced the drink, lived by its use to a hundred years free from any disease.
The Oat is a native of Britain in its wild and uncultivated form, and is distinguished by the spikelets of its ears hanging on slender pedicels. This is the Avena fatua, found in our cornfields, but not indigenous in Scotland. When cultivated it is named Avena sativa. As oats needs less sunshine and solar warmth to ripen the grain than wheat, they furnishes the principal grain food of cold Northern Europe.
With the addition of some fat this grain is capable of supporting life for an indefinite period. Nevertheless the Oat did not enjoy a good reputation among the old Romans.
American doctors have taken of late to extol the Oat (Avena sativa) when made into a strong medicinal tincture with spirit of wine, as a remarkable nervine stimulant and restorative: this being "especially valuable in  all cases where there is a deficiency of nervous power, for instance, among over-worked lawyers, public speakers, and writers."
The tincture is ordered to be given in a dose of from ten to twenty drops, once or twice during the day, in hot water to act speedily; and a somewhat increased dose in cold water at bedtime so as to produce its beneficial effects more slowly then. It proves an admirable remedy for sleeplessness from nervous exhaustion, and as prepared in New York may be procured from any good druggist in England. Oatmeal contains two per cent. of protein compounds, the largest portion of which is avenin. A yeast poultice made by stirring Oatmeal into the grounds of strong beer is a capital cleansing and healing application to languid sloughing sores.
Oatmeal supplies very little saccharine matter ready formed. It cannot be made into light bread, and is therefore prepared when baked in cakes; or, its more popular form for eating is that of porridge, where the ground meal becomes thoroughly soft by boiling, and is improved in taste by the addition of milk and salt. "The halesome parritch, chief of Scotia's food," said Burns, with fervid eloquence. Scotch people actually revel in their parritch and bannocks.
"We defy your wheaten bread," says one of their favourite writers, "your home-made bread, your bakers' bread, your baps, rolls, scones, muffins, crumpets, and cookies, your bath buns, and your sally luns, your tea cakes, and slim cakes, your saffron cakes, and girdle cakes, your shortbread, and singing hinnies: we swear by the Oat cake, and the parritch, the bannock, and the brose." Scotch beef brose is made by boiling Oatmeal in meat liquor, and kail brose by cooking Oatmeal in cabbage-water.
Crushed Oatmeal, from which the husk has been removed, is known as "groats," and is employed for making gruel. At the latter end of the seventeenth century this was a drink asked-for eagerly by the public at London taverns. "Grantham gruel," says quaint old Fuller, in his History of the Worthies of England, "consists of nine grits and a gallon of water." When "thus made, it is wash rather, which one will have little heart to eat, and yet as little heart by eating."
But the better gruel concocted elsewhere was "a wholesome Spoon meat, though homely; physic for the sick, and food for persons in health; grits the form thereof: and giving the being thereunto." In the border forays of the twelfth and thirteenth centuries all the provision carried by the Scotch was simply a bag of Oatmeal. But as a food it is apt to undergo some fermentation in the stomach, and to provoke sour eructations. Furthermore, it is somewhat laxative, because containing a certain proportion of bran which mechanically stimulates the intestinal membranes: and this insoluble bran is rather apt to accumulate.
Oatmeal gruel may be made by boiling from one to two ounces of the meal with three pints of water down to two pints, then straining the decoction, and pouring off the supernatant liquid when cool. Its flavour may be improved by adding raisins towards the end of boiling, or by means of sugar and nutmeg. Because animals of speed use up, by the lungs, much heat-forming material, Oats (which abound in carbonaceous constituents) are specially suitable as food for the horse.