Oleum Morrhuae (U. S. P.)—Cod-Liver Oil.
Preparation: Emulsion of Cod-Liver Oil
"A fixed oil obtained from the fresh livers of Gadus Morrhua, Linné, and of other species of Gadus (Class, Pisces; Order, Teleostia; Family, Gadida). It should be kept in well-stoppered and perfectly dry bottles"—(U. S. P.).
SYNONYMS: Oleum jecoris aselli, Cod oil, Oleum hepatis morrhuae.
Source and History.—The common codfish is the Gadus Morrhua of Linnaeus, or Morrhua vulgaris and Asellus major of other naturalists. It is a fish 2 or 3 feet in length, having a gray back with yellowish spots, and a white abdomen. The body is somewhat flattened, and symmetrical; the ventral fins are pointed and placed under the throat. There are 3 dorsal and 2 anal fins, and a cirrus or beard at the end of the snout. The teeth are pointed and unequal, and are disposed in several rows. The large gills are 7-rayed. On the external surface of the body are scales, rather soft, and not of large size. It is an inhabitant of cold or temperate seas, and is found, at certain seasons of the year, in abundance on the coast of Norway, in the neighborhood of Iceland, in the Russian Arctic Sea, and on the New England and Newfoundland coasts. The Norwegian oil, from the Lofoten Archipelago, is the most famous, and much of it is consumed in this country; but in recent years, the oil from the Newfoundland coast is gradually gaining in favor, owing to improvements in its manufacture. Other species of Gadus from which cod-liver oil is sometimes obtained, are coal-fish (G. carbonarius, Linné, or Merlangus carbonarius, Cuvier), dorsch, or dorse (G. callarius, Linné), turbot (Rhombus maximus, Cuvier), and occasionally from the pollack (Gadus pollachius, Linné, or Merlangus pollachius, Cuvier), hake (Gadus Merluccius, Linné, or Merluccius communis, Cuvier), whiting (Gadus Merlangus, Linné, or Merlangus vulgaris, Cuvier), ling (Gadus Molva, Linné, or Lota Molva, Cuvier), and haddock (Gadus aeglifinus, Linné). In the Lofoten Islands, the codfish come in innumerable quantities in the month of January to deposit their spawn, all other fishes disappearing as if by enchantment. The codfishing commences about the early part of January and terminates about the middle of April; there being no less than 25,000 persons engaged in the business, and the quantity of the fish is prodigious, incalculable. The annual production in the Lofoten Archipelago alone is on an average about 400,000 gallons. Three barrels of liver yield 1 barrel of first quality oil, and ½ barrel of brown oil obtained by heat and expression. (For details regarding the Norwegian codfisheries, we refer those interested to an exceedingly readable monograph entitled Codliver Oil and Chemistry, published quite recently, by Dr. F. Peckel Möller, London and Christiania, 1895.) Among many other items of interest, it is demonstrated how the peculiar formation of the Norway seaboard together with the habits of the codfish serves to make the Lofoten Islands the natural center of the Norwegian fisheries. (Also see résumé of the commerce in cod-liver oil and its chemistry, by J. H. Stallmann and E. H. Gane, in Amer. Drug., Jan., 1899, pp. 37-40.)
Preparation.—The principal process by which the oil is now prepared is to remove blood and impurities from the carefully sorted livers by repeated washings; then the gall-bladder is removed and the livers, as soon as practicable, are put into iron kettles and subjected to steam heat with constant stirring. The oil separates from the liver tissue, and, after decantation and filtration through a funnel, is drawn off into barrels. In the Newfoundland fisheries, the oil obtained by steam heat is exposed to intense cold until it is partly solidified; the mass is then put into bags and subjected to strong pressure. In this manner the American shore oil is obtained. The residual stearin is sold to soap-makers.
Description.—Three kinds of cod-liver oil are usually met with in commerce: The white or pale-yellow, which is obtained from fresh and perfectly healthy livers (shore oil). It is the official oil and is described by the U. S. P. as "a pale-yellow, thin, oily liquid, having a peculiar, slightly fishy, but not rancid odor, and a bland, slightly fishy taste. Specific gravity, 0.920 to 0.925 at 15° C. (59° F.). Scarcely soluble in alcohol, but readily soluble in ether, chloroform, or carbon disulphide; also in 2.5 parts of acetic ether"—(U. S. P.). The second form is pale-brown, or brownish-yellow (straits oil); less care is exercised in the selection of the livers and the preparation of the oil. The third kind is dark-brown (banks oil), and is an inferior grade, being derived from putrefied livers; its odor is disagreeable, its taste acrid and bitter; and it has an acid reaction. The best grade is universally preferred in the United States.
Adulterations and Tests.—Cod-liver oil is subjected to adulterations in several ways. One method is to bleach an inferior, dark oil, it is stated, by exposure to the rays of the sun. The addition of mineral oils can be recognized by saponification which leaves the adulterant unaffected. An oil that has undergone partial putrefaction may be judged by the quantity of free volatile acids in the oil. Such oils also absorb much less iodine than fresh cod-liver oil. Refined seal oil and seed oils are also used as adulterants of cod-liver oil. (For a more detailed consideration of this phase of the subject, see special works on analysis, e.g., A. H. Allen, Commercial Organic Analysis, Vol. II, Part I, 3d ed., 1899, p. 197.) The U. S. P. gives the following tests for the purity of cod-liver oil: "If 1 drop of the oil be dissolved in 20 drops of chloroform, and the solution shaken with 1 drop of sulphuric acid, the solution will acquire a violet-red tint, rapidly changing to rose-red and brownish-yellow. If a glass rod, moistened with sulphuric acid, be drawn through a few drops of the oil, on a porcelain plate, a violet color will be produced. Cod-liver oil should be only very slightly acid to litmus paper previously moistened with alcohol (limit of free fatty acids). When the oil is allowed to stand for some time at 0° C. (32° F.), very little or no solid fat should separate (absence of other fish oils, and of many vegetable oils). If 2 or 3 drops of fuming nitric acid be allowed to flow alongside of 10 or 15 drops of the oil, contained in a watch-glass, a red color will be produced at the point of contact. On stirring the mixture with a glass rod, this color becomes bright rose-red, soon changing to lemon-yellow (distinction from seal oil, which shows at first no change of color, and from other fish oils, which become at first blue, and afterward brown and yellow"—(U. S. P.). The presence of seal oil may also be detected by means of Amagat and Jean's oleo refractometer (see Proc. Amer. Pharm. Assoc., 1898, p. 888).
Chemical Composition.—For a chronological history of the chemical study of cod-liver oil, see M. P. Heyerdahl in F. Peckel Möller's monograph above mentioned. According to older analyses, especially by De Jongh (1843), cod-liver oil was accepted to consist of about 19 to 26 per cent of palmitin and stearin, 72 to 76 per cent of olein, and from 2 to 5 per cent of non-fatty matters. The following substances have been observed in cod-liver oil in minor quantities, although the presence of many are no doubt due to putrefactive changes in the liver:
(1) Volatile acids (valerianic, Spaarmann, 1828, acetic and butyric acids, De Jongh); (2) iodine (De l'Orme, 1836; on an average only 0.000322 per cent, Stanford, 1884); (3) bromine (Herberger, 1839); (4) phosphorus (De Vrij, 1838); (5) biliary constituents (De Jongh, 1843; this is not confirmed by subsequent researches; if the gall-bladders are excluded from the process, no bile reaction can be obtained in cod-liver oil; Buchheim, 1884, Salkowsky, 1887); (6) cholesterin (Allen and Thompson, 1885; 0.46 to 1.32 per cent); (7) lipochrome (of W. Kühne, to which, in part, the color reaction with sulphuric acid is due; Salkowsky, 1887); (8) volatile bases: butyl-amine, amyl-amine, hexyl-amine, dihydro-lutidine; (9) non-volatile alkaloids—aselline (C25H32N4) and morrhuine (C19H27N3), both occurring only in the darker oils; (10) crystallizable morrhuic acid (C9H13NO3), a pyridine derivative, existing in the oil to the extent of 0.1 per cent. (Numbers 8, 9 and 10 were observed by Gautier and Mourgues, 1888; the existence of alkaloids in light-brown Norwegian oil, as well as in Newfoundland and Maine oils, was also confirmed by J. O. Schlotterbeck, Pharm. Jour. Trans., Vol. XXV, 1895, p. 585, from Pharm. Era.) A solid, fatty acid, gadinic acid, melting at 63° to 64° C. (145.4° to 147.2° F.), was obtained by Luck, in 1856, from a deposit in cod-liver oil. Morrhuol is an alcoholic extract of cod-liver oil obtained by Chapoteaut (Amer. Jour. Pharm., 1886, p. 19).
According to M. P. Heyerdahl's researches, published in the monograph aforementioned, pure cod-liver oil contains no stearin, no olein, and only about 4 per cent of palmitic acid as tri-palmitin. Two new glycerides, however, were discovered, namely, 20 per cent of tri-therapin, the glyceride of therapic acid (C17H26O2), a hitherto unobserved, unsaturated fatty acid containing four double bonds, and forming an octo-bromine addition product (C17H26Br8O2); and over 20 per cent of tri-jecoleïn, the glyceride of jecoleïc acid (C19H36O2) which contains only one double bond, and is isomeric with doeglic acid. The remainder of the oil contains glycerides with one or more unsaturated acids belonging to the same series as jecoleïc acid, but as yet entirely unknown. The solid fat removed in the manufacture of cod-liver oil by cooling and subsequent pressure, and believed to be stearin, probably contains chiefly these undetermined acids. Therapic and jecoleïc acids, both free and as glycerides, become rapidly oxidized when exposed to air, especially if heated at the same time. They are converted into hydroxyacids which the author demonstrates to be the cause of rancidity in the oil, hitherto ascribed to the presence of free fatty acids. These hydroxyacids are thus shown to be physiologically undesirable, hence the necessity of absolutely excluding the air in the preparation of the oil; this is done by a patented process, in which an inert gas (carbonic acid) remains in contact with the oil during its manufacture.
Action, Medical Uses, and Dosage.—Cod-liver oil is nutritive and alterative. It has long been used as a domestic remedy in chronic rheumatic and strumous diseases, especially in the northern parts of Europe, and has been in general medicinal use only since the treatise upon it by Prof. Bennett, of Edinburgh, in 1841, although employed occasionally in the profession as early as 1766. Cod-liver oil is a remedy for defective nutrition, and when tolerated can be relied upon to give good results; but if it provokes persistent nausea, vomiting, disgust, and diarrhoea, it can not be expected to be other than harmful. Cod-liver oil is a fat-producing agent, excelling other fats which have been proposed as substitutes for it, in digestibility. When cod-liver oil "is kindly received by the stomach it increases the quantity of red corpuscles, improves the appetite and general strength, and the pulse becomes full and strong, flesh increases, and nutrition is improved" (Locke's Syllabus of Mat. Med., p. 346). Though used for many conditions, it has been shown to do the most good in the poorly nourished, suffering from phthisis pulmonalis, tabes, rickets, chronic bronchitis, and chronic rheumatism in the scrofulous. It is not necessarily a curative agent, but in many conditions it tides the patient over while other agents exert their curative effects. In tubercular arthritis, and so-called scrofulous inflammations of the joints, its influence is often marked. Where there is necrosis, however, it effects are less evident. It may be given in tabes mesenterica when there is emaciation, a hard abdomen, offensive breath, and cough. When epilepsy depends upon a scrofulous and debilitated condition, cod-liver oil often proves a good remedy (Locke). In rickets, given internally and applied locally to the spine, it is one of our best remedies. Fistula in ano, scrofulous enlargements, and scrofulous ulcerations call for it. It undoubtedly prolongs the consumptive's life, but it should not be forced if the stomach persistently refuses to tolerate it. In some cases it does not seem to derange the stomach, but nauseates by its unpleasant taste. In these cases the difficulty is sometimes overcome by persisting in the use of the remedy or by changing from one to another preparation of the oil. In all cases where it can be tolerated, the pure oil should be preferred over the emulsions.
The diseases, besides those enumerated, in which it is said to be most efficient, are strumous diseases, strumous ophthalmia, pseudo-syphilis, in scrofulous constitutions, and various chronic cutaneous diseases, as in eczema, impetigo, prurigo, lichen, squamous affections, pityriasis, ichthyosis, etc. Gout, and occasionally caries, it is said, have yielded to its influence. It is also asserted to have been found useful in diseases of the joints and spine, lupus, obstinate constipation, worms, and incontinence of urine; and may be advantageously employed in all chronic cases, in which the disease appears to consist mainly in impaired digestion, assimilation, and nutrition. Externally used in opacities of the cornea, a drop or two placed on the cornea with a camel's-hair pencil; also in various chronic cutaneous diseases, rhagades, chaps, eczema, excoriations, and fissures. Its use is contraindicated in plethora, or where there is a strong tendency to it, lest hemorrhage be provoked. When long used, it is said to frequently occasion an eruption on the surface of an eczematous character. But little advantage will be apparent from the administration of cod-liver oil, until its use has been persevered in for 5 or 6 weeks, though it often commences earlier. The light-colored oil is the best. Some prefer the darker colored oils. The dose of cod-liver oil is ½ fluid ounce, twice a day, or more; but it is best to begin with small doses at first, say 1 drachm only, in order to lessen the risk of nausea and vomiting. Patients soon accustom themselves to its use without repugnance. It is best given alone, followed by some claret, or a little sugar and cinnamon powder, or prepared with aromatic oils, the same as castor oil (which see). It may be given in coffee, milk, or brandy, and for consumptives in Bourbon. A pinch of salt sometimes renders it palatable, while others advise the chewing of a small portion of smoked herring. Tomato catsup, and particularly the froth of malted beverages appears to mask the unpleasantness of the oil. (For various methods of rendering the oil palatable, see Emulsio Olei Morrhuae.)
Dr. Alexander Wallace recommends a mixture of equal parts of lime-water and cod-liver oil, well shaken together, as a tonic, sedative, antacid, and nutrient; it forms a thick, milky emulsion, palatable, especially when taken with a little sherry wine, and may be used in all the forms of disease in which cod-liver oil is recommended.
In Germany a ferruginous cod-liver oil is much employed; it is prepared by first making a soda soap, from which its glycerin is removed by concentrated solution of sea salt, giving as the result an iron soap by double decomposition—this last soap is dissolved in sixteen times its weight of cod-liver oil. The oil thus prepared is brown and holds in solution 1/500 of iron, the taste of which is hardly discernible.
Related Oils.—OLEUM RAJAE, Ray, or Skate oil. From the livers of Raja Batis, Linné. Specific gravity, 0.928. Odor and taste, fishy; color, bright or pale-yellow; reaction, neutral. Said to contain a greater quantity of iodine than cod-liver oil. It is used by the Belgians and French as a substitute for cod-liver oil.
OLEUM BALAENAE, Whale oil, Train oil.—Obtained from the blubber of Balaena mysticetus, Linné, Greenland whale; and Balaena australis, Desmoulins, Cape whale. Specific gravity, 0.926. Odor, fishy; taste, disagreeable. At 10° C. (50° F.) it deposits a solid material, palmitin. Some whale oils contain notable quantities of valerin.
MENHADEN OIL.—Obtained on the New England coast from the Alosa Menhaden, Cuvier. It constitutes one of the oils known as the fish oils or whale oils, and is used in the manufacture of leather. The term train oils now includes all oils from the fleshy parts of the seal, shark, cod, and like fishes or marine mammals.
OLEUM SQUALI, Shark oil.—Specific gravity varies from 0.911 to 0.928. Taste, acrid; color, pale-yellow. At -6° C. (21.2° F.) it is still a limpid fluid. It is obtained from the liver of Squalus Carcharias, Linné, or Shark, besides some other related species. The livers of Pastinaca hastata, De Kay, or American stingray, also yield an oil by expression. From 0.7 to 17.3 per cent of cholesterol (cholesterin) have been obtained from six specimens of shark oil by A. H. Allen (Org. Chem. Anal., Vol. II, Part I, 3d ed., p. 200).
OLEUM CETI, Sperm oil.—Found in the cranial cavity of the Physeter macrocephalus, Linné, or Sperm whale, and obtained by expression. Specific gravity, about 0.879. Color, yellow or brownish-yellow. It is distinguished from the oils of the Whale-oil group by its lower specific gravity and its composition. Upon cooling, spermaceti is deposited. Sperm oil proper yields, upon saponification, chiefly oleic acid and dodecatyl alcohol (C12H25OH). It is a valuable lubricant.
OULACHON OIL, or EULACHON OIL.—A proposed substitute for cod-liver oil, yielded abundantly by the Candle-fish (Thalicthys pacificus) of the north Pacific coast. Congelation of this oil begins at -7° C. (19.4° F.), though according to some statements it is of the consistence of lard at common temperatures. Specific gravity, 0.907 at 15.5° C. (60° F.). It contains oleic acid (60 per cent), stearic, and palmitic acids (20 per cent), and non-saponifiable matter (about 13 per cent).
DUGONG OIL.—The Dugong (Halicore Dugong, Cuvier) is an herbivorous mammal found in shallow waters throughout the Indian seas. There are two species of them—the Malay or Indian Dugong (Halicore indicus), and the Australian (Halicore australis). They are from 6 to 16 feet in length, and weigh from 400 to 600 pounds upon an average; occasionally, however, they are found of larger size. They frequent the neighborhood of ocean inlets where sea-grass, algae, and fuci abound, and the water is shallow. They are called Sea-hogs, and their flesh (intermediate in flavor between beef and pork), is esteemed a great delicacy by the natives of the islands and countries near which the animal abounds. Underneath the skin (which is about ½ inch in thickness, and is often made into gelatin) is found a layer of adipose tissue, which yields from 4 to 16 gallons of oil, according to the size of the dugong. This oil is very palatable, and is acceptable to the most sensitive stomach, and has obtained somewhat of a reputation as a substitute for cod-liver oil. The oil is fully as nutritious as cod-liver oil, and may be administered in all forms of tuberculous and wasting diseases, and with equal advantage in cases where there is a decided repugnance to the cod-liver oil (J. King).
TURTLE OIL.—This oil is said to be fully as efficacious as cod-liver oil in malnutrition, especially in strumous individuals. Large quantities of it are consumed in South America, where it is prepared from turtle-eggs; in Jamaica and the Seychelle Island it is prepared from turtle-fat.