This section is from the book "Meals Medicinal", by W. T. Fernie. Also available from Amazon: Meals Medicinal: With "Herbal Simples" Curative Foods From the Cook in Place of Drugs From the Chemist.
Our invaluable Potato, which enters so largely into the dietary of all classes, claims consideration here chiefly as regards its curative uses, and medicinal capabilities. It belongs to the natural order of Solanaceous plants, so called because of their sedative properties tending "solare," to lull pain, though poisonous. The underground tubers, or starch stores, of the Potato plant are its edible parts, whilst the stalks, leaves, and green berries share the narcotic, and noxious attributes of this Nightshade (solanaceous) tribe. No daylight reaches the underground tubers so as to develop any poisonous tendencies therein. But the young shoots derive solanin from the early tubers; and in spring time young green Potatoes, if exposed to daylight, are made poisonous thereby, and have a disagreeable taste. There are two sorts of Potato tubers, - the red, and the white. A roasted Potato takes two hours to digest; a boiled one three hours and a half. Chemically the Potato contains citric acid, like that of the lemon, this being of admirable use against scurvy, or rickets in children; likewise salts of potash, which have a similar beneficial action; also phosphoric acid, yielding phosphorus in a quantity less only than what is afforded by the apple, and by wheat.
It is of the first importance that the potash salts should be retained by the Potato during its cooking, and therefore the tubers must be steamed in their jackets; else, if peeled, and then steamed, they lose respectively 7 and 5 per cent of potash, and phosphoric acid; if boiled after peeling they lose as much as 33 per cent of potash, and 23 per cent of phosphoric acid. It is evident that the tough skin of the Potato must resist the escape of the potash salts into the water, though it may not completely prevent it. The bursting of the skin occurs only at quite the latter stage of the cookery. Potatoes are deficient in albuminoids, and phosphates. Small Potatoes were Athenians' "meat." But, as regards Potatoes of good quality, and skilfully cooked, "picture to yourself the ' ball of flour,' as old-fashioned housewives call it, "lying in the dish, perfectly steamed, diffusing the softest, subtlest aroma, ready to crumble, all but to melt, so soon as it is touched. Recall the gust, and its after-gust, blending so consummately with that of the joint, hot, or cold.
Then think of this same Potato cooked in any other way, and what sadness will come upon you! As for ' pommes de terre sautes,' 'pommes de terre Lyonnaise,' 'pommes de terre frites,' can any of these compare with the 'plain ball of flour' for a moment?" "The roots" (tubers), says Gerarde, "were forbidden in Burgundy, for that they were persuaded the too frequent use of them causeth the leprosie".
But it is now believed that the Potato has had much to do with banishing leprosy from England. The said affliction has become restricted to countries where the Potato is not grown. The peel, or rind, of a Potato contains the poisonous substance known as "solanin," which is dissipated, and rendered inert therein when the whole unpeeled Potato is boiled, baked, or steamed; also dry heat serves to destroy it. Stupes of hot Potato-water obtained in this way are of external service in some forms of painful rheumatism. To make a decoction for such purpose, boil one pound of Potatoes in their coats, but each divided into four quarters, in two pints of water slowly down to one pint; then foment the swollen, and tender parts with this decoction as hot as it can be borne. Puerile as it may seem, the carriage of a small raw potato in the trouser's pocket, or beneath the breast of a woman's dress, has been often found to prevent rheumatism in a person predisposed thereto, - probably in a measure because of the sulphur which is present in the tuber, and of the narcotic principles present in the peel. Ladies in former times had their dresses supplied with special little bags, or pockets, in which to carry one, or more small, raw Potatoes about their person, for avoiding rheumatism.
If peeled, and pounded in a mortar, uncooked Potatoes applied cold make a very soothing cataplasm to parts which have been scalded, or burnt. These tubers are composed mainly of starch, which as a food affords elements for fatness, and for maintaining the animal warmth of the body; but the proportion of muscle-forming nourishment is but small; so that in this respect as much as ten and a half pounds of the tubers are required to equal one pound of butcher's meat as to proteid value. The Irish believe that an abundant Potato diet promotes fertility.
New Potatoes do not as yet furnish citric acid; their starch is immature, and not readily acted on by the saliva in the mouth during mastication. "The man of superior intellect," said Tennyson (justifying his love of boiled beef with new Potatoes), "knows what is good to eat." Likewise "think of the said new Potatoes! Our cook when dressing them puts into the saucepan a sprig of green mint. This is genius! No otherwise could the flavour of the vegetable be so perfectly, yet so delicately emphasized! The mint is there, and we know it; yet our palate knows only the young Potato" (H. Ryecroft). By fermentation fully-grown Potatoes, through their starch undergoing conversion into sugar, yield a wine from which may be distilled Potato-spirit, with a volatile oil therein called by the Germans Fuselol This is nauseous, and causes a heavy headache, with indigestion, and biliary disturbance, together with nervous tremors. Chemically it is amylic ether, being oily in appearance, with a strong smell, and an acrid taste. Because Potatoes, when coming into contact with yeast, undergo fermentation, they are employed by bakers in making bread, and increasing its aeration, - one peck of the "fruit" to each sack of flour.
By the Bread Acts of 1822, and 1833, which are still in force, it remains imperative that "every person who shall make for sale, or sell, or expose for sale any bread made wholly, or partially of peas, or beans, or Potatoes, or any sort of corn or grain other than wheat, shall cause all such bread to be marked with a large Roman M, signifying ' mixture,' (also ' mysteries ')." "It would be well, therefore," says The Lancet (1903), "to occasionally examine all loaves for this imprint." Sydney Smith wrote alliteratively:
"Two large Potatoes passed through kitchen sieve Unwonted softness to a, salad give".
And Sir Thomas Overbury said wittily about a dolt who took credit for the merits of his ancestors, "Like the Potato, all that was good about him was underground".