SEA SICKNESS. The most effectual preventive of sea sickness appears to be the horizontal position. When there is much pain, after the stomach has been well cleared, a few drops of laudanum may be taken, or an opium plaster may be applied over the region of the stomach. Persons about to proceed to sea should put their stomach and bowels in proper order, by the use of mild aperients, and even an emetic, if required, when it will generally be found that a glass of warm and weak brandy-and-water, to which 15 or 20 drops of laudanum, or, still better, 1 or 2 drops of creasote, have been added, will effectually prevent any disposition to sea sickness, provided the bowels be attended to, and excess in eating and drinking be at the same time avoided. A spoonful of crushed ice, in a wine-glassful of cold water, or weak brandy-and-water, will often afford relief when all other means fail. Smoking at sea is very apt to induce sickness. M. F. Curie, in the ‘Comptes Rendus,’ asserts that drawing in the breath as the vessel descends, and exhaling it as it ascends, on the billows, by preventing the movements of the diaphragm acting abnormally on the phrenetic nerves, prevents sea sickness. On this Mr Atkinson, at one of the meetings of the British Association, observed that—if a person, seated on board ship, holding a tumbler filled with water in his hand, makes an effort to prevent the water running over, at the same time allowing not merely his arm, but also his whole body, to participate in the movements, he will find that this has the effect of preventing the giddiness and nausea that the rolling and tossing of the vessel have a tendency to produce in inexperienced voyagers. If the person is suffering from sickness at the commencement
of his experiment, as soon as he grasps the glass of liquid in his hand, and suffers his arm to take its course and go through the movements alluded to, he feels as if he were performing them of his own free will, and the nausea abates immediately, and very soon ceases entirely, and does not return so long as he suffers his arm and body to assume the postures into which they seem to be drawn. Should he, however, resist the free course of his hand, he instantly feels a thrill of pain, of a peculiarly stunning kind, shoot through his head, and experiences a sense of dizziness and returning nausea.
Dr Doring, a Viennese physician, states that an ordinary dose of chloral hydrate is an unfailing remedy for sea sickness. In various cases recorded by him it seems to have been of the greatest service, even during long sea voyages, ensuring a good night’s rest, arresting violent sickness when it has set in, and preventing its return.
SEDATIVE PILLS, Gunther’s. These are composed of the following ingredients:—Assafœtida powder, 50 parts; extract of valerian, 50; extract of belladonna, 3; oxide of zinc, 1 part; castor, 2 parts. Make into a pill-mass, to be administered in doses of 3 to 10 grains, twice daily, in chorea, &c.
SED′ATIVES. Syn. Sedativa, L. Medicines and agents which diminish the force of the circulation or the animal energy, and allay pain. Foxglove, henbane, tobacco, potassio-tartrate of antimony, and several of the neutral salts and acids, act as sedatives. Cold is, perhaps, the most powerful agent of this class.
SEED. Syn. Semen, L. The seeds of plants are conspicuous for their vast number and variety, and their extreme usefulness to man. The seeds of certain of the Graminaceæ furnish him with his daily bread; some of those of the Leguminosæ in either the immature or ripe state, supply his table with wholesome esculents, or provide a nourishing diet for his domestic animals; whilst those of numerous other plants, dispersed through every class, orders, and family, yield their treasures of oil, medicinals, or perfumes for his use.
SELEN′IC ACID. H2SeO4. Syn. Acidum selenicum, L. Prep. By fusing selenium with nitrate of potassium or of sodium, acting on the fused mass with water, precipitating the resulting solution with acetate or nitrate of lead, and decomposing the precipitate (selenate of lead), diffused in water, with sulphuretted hydrogen. The selenic acid, thus obtained, may be cautiously concentrated in a glass vessel, if necessary; but if this be pushed too far, it is resolved into selenious acid (H2SeO3) and oxygen.
Prop., &c. Hydrated selenic acid is a colourless liquid, closely resembling sulphuric acid; its salts (selenates) bear the closest analogy to the sulphates.
Selenic Acid (H2SeO4). No selenic anhydride is known. Selenic acid may be obtained in solution by deflagrating selenium or a selenite with potassic nitrate. The residue dissolved in water is mixed with a solution of plumbic nitrate, an insoluble plumbic seleniate being precipitated. The plumbic seleniate is suspended in water and decomposed by means of a current of sulphuretted hydrogen. Plumbic sulphide is precipitated, and the liberated selenic acid separated by filtration is concentrated until it acquires a sp. gr. of 2·6; if heated above 554° F. it decomposes into selenious anhydride, water, and oxygen. Selenic acid has a great resemblance to sulphuric acid. It acts upon the metals in the same manner, and even dissolves gold. The seleniates are also very similar in properties to the sulphates, and both classes of salts are isomorphous. The seleniates give the same characteristic odour before the blowpipe as the selenites. Their solutions give white precipitates with the salts of barium, strontian and lead, insoluble in nitric acid. If a soluble seleniate is boiled with hydrochloric acid, selenic acid is set free, and is reduced to selenious acid, sulphurous acid will then precipitate reduced selenium from the solution. Baric seleniate may be also decomposed in a similar manner, and this reaction distinguishes it from baric sulphate.
SELE′NIUM. Se. A rare chemical element, discovered by Berzelius in 1817 in the refuse of a sulphuric acid manufactory near Fahlun, in Sweden, it having been derived from the pyrites employed in the manufacture of the acid. Hence the pyrites of Fahlun forms the chief source of this rare body, although it exists, but less abundantly, in combination with a few other metals, termed selenides. Selenium is chiefly interesting to the chemist from its remarkable analogy in chemical properties to sulphur. Like this latter element, it is capable of assuming three allotropic forms—the amorphous, the vitreous, and the crystalline.