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portion is exposed and becomes dissolved; hence starch is said to be insoluble in cold, but soluble in boiling water. Starch is CHO, and is classed with the carbohydrates. By the action of heat, or by long boiling with diluted sulphuric or hydrochloric acid, it is converted into dextrin, an isomeric soluble principle, and by the same process this may be converted into grape sugar. The same change takes place in grains, after germination, through the agency of a nitrogenous principle termed diastase. The test for starch is iodine, which forms with starch-solution a rich blue iodide; with bromine starch strikes an orange precipitate; nitric acid converts it into oxalic acid.

Effects and Uses.-The starchy or farinaceous articles form an important group of nutrients. Their assimilation is effected by the albuminous principles of the digestive tube (salivin, pancreatin, etc.), which change starch into grape sugar. This is converted in part into fatty tissue, and is partly fermented into lactic acid, which acts as a calefacient. Starch is used externally as a dusting powder to excoriated surfaces, as an emollient poultice, and in solution as a vehicle for laudanum as an enema. It is the antidote for iodine.

GLYCERITUM AMYLI (Glycerite of Starch) (Plasma) contains 10 per cent. of starch thoroughly mixed with glycerin and dissolved by the aid of heat. It is excellent as a vehicle for astringent applications in ophthalmic surgery (Bartholow), and as an application to allay the heat, burning and itching of the skin in scarlatina and small-pox; in the latter it is particularly pleasant to the patient, and has as much effect in preventing pitting as any other application (H. M.). It is used as a substitute for ointments, and is a good excipient for pills. Amylum iodatum (iodized starch) has been already spoken of (vide 376).

ICHTHYOCOLLA (Isinglass), prepared from the swimming bladder of Acipenser Huso (the sturgeon) and of other species of Acipenser (Class, Pisces; Ord. Sturiones) is the purest form of gelatin. Court plaster (Emplastrum ichthyocolle) is made by coating oiled silk with a solution of isinglass. Gelatin is also used as an article of diet, and is employed in pharmacy to

make capsules for the administration of disagreeable liquid medicines, and as a coating for pills.

For external use, the ANIMAL FATS are employed as emollients. When applied externally, they are absorbed and assimilated, and increase the body weight; hence inunctions have been practiced in wasting diseases, as phthisis, etc. They also reduce the temperature of the body in febrile conditions, and allay itching and irritation of the surface, and for this purpose they are employed in the exanthemata. They are also used as excipients for other medicines, in making ointments, etc.

ADEPS (Lard) is the PREPARED FAT of Sus Scrofa (the hog); the internal fat of the abdomen is preferred, which is washed, melted and strained. Below the temperature of 90° it occurs as a soft, white solid, which for medicinal use should be free from saline matter. It consists of olein and stearin. It is used in pharmacy as an addition to poultices, and as an inunction in the exanthemata, particularly scarlatina. Cerate (ceratum) is made by melting together 70 parts of lard and 30 parts of white wax. Unguentum (ointment) is made by melting together 80 parts of lard and 20 parts of yellow wax. Lard oil (the olein of lard) is a good vehicle for anodyne enemata.

Adeps benzoinatus (benzoinated lard), formerly termed benzoinated ointment, consists of benzoin 2 parts in 100 parts of lard.

SEVUM (Suet) is the INTERNAL FAT OF THE ABDOMEN of Ovis Aries (the sheep) (Class, Mammalia; Ord., Ruminantia), purified by melting and straining. It is composed almost exclusively of stearin, but also contains some palmitin, olein and hircin.

CETACEUM (Spermaceti) is a peculiar CONCRETE FATTY SUBSTANCE obtained from Physeter macrocephalus or spermaceti whale (Class, Mammalia; Ord., Cetacea). It consists almost entirely of cetyl palmitate (C16H33-C18H31O2) or cetin, but recently has been shown to contain also ethers of stearic, myristic and laurostearic acids; and of the alcohols, lethal (C12H2O), methal

34

(CHO), ethal (C16H3) and stethal (CHO). Spermaceti cerate (ceratum cetacei) is made by melting together 10 parts of spermaceti and 35 parts of white wax, and then adding 55 parts of olive oil, previously heated. Ointment of rose-water (see p. 165) contains spermaceti.

CERA FLAVA (Yellow Wax) is a peculiar CONCRETE SUBSTANCE prepared by Apis mellifica, the honey bee (Class, Insecta; Ord. Hymenoptera).

CERA ALBA (White Wax) is yellow wax bleached. They are used chiefly in making cerates, ointments and plasters.

ACIDUM OLEICUM-OLEIC ACID.

Oleic acid (HC18H3O2) exists in nature combined with glycerin as olein. It is obtained in an impure state as a secondary product at stearin candle manufactories. To purify the acid, it is cooled to 14° F. and expressed; the solid portion melted and treated with lead protoxide; the lead oleate is dissolved out by ether, decanted, and shaken with hydrochloric acid, which decomposes it; the ethereal layer is decanted and evaporated. The oleic acid thus obtained is still contaminated with a little oxyoleic acid, which is difficult to separate. Oleic acid is a yellowish oily liquid, which becomes brownish and rancid by exposure to the air, without smell or taste, soluble in alcohol, ether and cold sulphuric acid, but insoluble in water. The oleates of the alkaline metals are soft soluble soaps; those of the earthy metals are insoluble in water, but soluble in alcohol and ether.

Oleic acid is used principally in preparing the oleates of veratrine (vide p. 204) and of mercury (vide p. 363).

OLEUM THEOBROMÆ-OIL OF THEOBROMA.

This oil, commonly known as Butter of Cacao, is the FIXED OIL EXPRESSED from the SEED of Theobroma Cacao (Nat. Ord. Sterculiaceae), a handsome tree, from twelve to twenty feet in height, growing in Mexico, the West Indies, Central America and South America. The fruit is an ovate-oblong capsule or

Theobromine
Cacao butter

berry, half a foot in length, with a thick, coriaceous, ligneous rind, inclosing a whitish pulp, in which numerous ovate seeds are embedded, about the size of an almond. Separated from the matter in which they are enveloped, these constitute the chocolate-nuts of commerce (see p. 98). They contain FIXED OIL (cacao butter), theobromine, and other matters. is a nitrogenous alkaloid, analogous to caffeine. is obtained by expression, decoction or the action of a solvent. It occurs in whitish or yellowish oblong cakes, of the consistence of tallow and of an agreeable odour and taste. It contains a large proportion of stearin, also palmitin and olein. It is used in pharmacy for coating pills, and also largely in preparing suppositories, for which it is well adapted from its consistence and blandness. It may be used with advantage as an unguent in fevers, to reduce the heat and allay the cutaneous irritation.

GLYCERINUM-GLYCERIN.

This is a substance which exists in oils in combination with the fatty acids (stearic, margaric, oleic, etc.), and is liberated from them when they unite with bases in the process of saponification. It was first obtained in the process for making lead plaster, by mixing litharge (lead protoxide) with olive oil and boiling water, by which the fatty acid unites with the lead and is precipitated, and the glycerin remains in solution. It is freed from any lead it may contain by means of a stream of sulphuretted hydrogen gas, and is afterwards filtered through animal charcoal; or, as it is now usually made more directly, by decomposing fats and distilling by steam under high pressure. Glycerin (C,H,3HO), or Glyceric Alcohol, is the hydrate of Glyceril, Glycil, or Propenyl, and is a triatomic alcohol. It is a thick, syrupy liquid, colourless or straw-coloured, unctuous to the touch, inodorous, and of a sharp, sweet taste. When pure its sp. gr. is 1.260, when it contains 95 per cent. of absolute glycerin; the Pharmacopoeia directs its sp. gr. to be 1.250. It is soluble in oils, alcohol and water, but is insoluble in ether and chloroform, and does not evaporate when exposed to the air, but absorbs one-half its weight of water. It has remark

able solvent properties, dissolving iodine, bromine, the alkalies, tannic and other vegetable acids, a large number of neutral salts, and many organic principles. Officinal solutions of medicinal substances in glycerin are termed glycerites (glycerita).

Effects and Uses.-Glycerin is a bland and unirritating substance. It has the capacity of diffusing itself freely over and through organic matter, incorporating itself between organic molecules, by which it is absorbed and appropriated. It has been used internally as a nutrient and demulcent, and has been deemed of value in cachectic, strumous and asthenic conditions in children, but the weight of opinion is against its efficacy as an alterative. It is as a topical application that it is chiefly employed. As an enema in dysentery, to soften hardened mucus in the air passages, in various cutaneous affections, in diphtheria, in deafness attended with dryness of the meatus, and as a vehicle or solvent for active medicines, glycerin is a valuable article. Guzzo (Gaillard's Med. J., March, 1882) recommends the following treatment to prevent extensive cicatrization following burns: apply to the whole burned surface a piece of lint thickly spread with cold cream and covered with a compress two inches thick saturated with glycerin (freshly wet from three to six times a day; the whole dressing to be changed daily), and covered with a dry compress and bandage. This treatment failed in only one of fifty-two cases (Archiv. Dermat., Oct., 1882).

Glyceritum amyli (glycerite of starch) has been already considered (vide p. 459).

Glyceritum vitelli (glycerite of yolk of eggs) (glyconin) is made by mixing thoroughly 45 parts of fresh yolk of egg with 55 parts of glycerin. It is a good vehicle for the administration of cod-liver oil, a few drops of some aromatic being added as a flavouring ingredient.

PETROLATUM.

Petrolatum is a mixture of hydrocarbons obtained by distilling the lighter and more volatile portion from American petroleum, and purifying the remainder. Mineral oils have