COD-LIVER OIL is an oil of great medicinal value, obtained from the liver of the common cod (Äsorrb,ua vulgaris), and also to some extent from the ling {Lota molva), the whiting (Merlangus vulgaris), the pollack {Merlangus polla- chius), as well as other members of the Gadidae. The oil obtained from the livers differs in quality from a very pure pale-coloured liquid to a dark evil-smelling product, according to the care exercised and the processes adopted for its extraction. The very dark coloured rank oils are used only for burning and lubricating, and in commerce are known as cod oil. The purer qualities, up to an oil having a brown sherry colour, are alone used medicinally as cod-liver oil. Various methods of extracting the oil are adopted in the different countries where its preparation is prosecuted. Generally it may be stated that the medicinal oil is obtained from selected livers, which are carefully examined, cleaned, split up, and thrown together into a large vessel’ From these a very small proportion of a pure and almost colourless oil exudes spontaneously, and exposure to the heat of the sun causes a further exudation. By the application of heat in a steam or water bath to a temperature not exceeding 180° Fahr., a proportion of still pale, or straw-coloured oil is obtained. The oil which results from the application of a higher heat and pressure, and that obtained from unhealthy and from putrid livers, are •only used industrially as cod oil. The extraction of the oil is most extensively prosecuted in Newfoundland and in Norway; but a considerable quantity is also prepared in the Shetland Islands and along the east coast of Scotland....
Three varieties of medicinal oil are recognized in commerce—pale, light brown, and brown; but these insensibly merge into each other, and are only the result of different processes or periods of preparation, as mentioned above. The pale oil possesses a fishy odour and a slightly acrid taste, while with the darker oil there is a distinctly disagreeable empyreumatic odour and taste. In composition the oil contains olein and margarin, with small proportions of free butyric and acetic acids, a peculiar principle termed gaduin, certain bile acids, free phosphorus, phosphatic salts, and traces of iodine and bromine. Cod-liver oil is valuable in medicine on account of its great nutrient properties; it adds rapidly to the store of fat within the human frame, and it enriches the blood in red corpuscles. It is much more digestible than other animal oils, a fact which may account for its superior therapeutic value. At one time it was supposed that its virtues resided in the iodine and bromine which the oil generally contains; but these are present only in exceedingly minute proportions, and sometimes they cannot be traced at all. The oil has long been favourably known in medicine as a remedy for rheumatic complaints, but its great value in pulmonary consumption has been demonstrated only in comparatively recent times. It is administered internally in chronic rheumatism, scrofula, phthisis, chronic skin diseases, and general debility; and it is sometimes externally applied in affections of the skin. The oil is taken with facility by young children; but the repugnance of adults to its taste and eructations is not easily overcome, and many methods have been suggested for masking its taste. With that view the oil is enclosed in gelatinous capsules, or prepared in the form of aromatized emulsions, of equal parts of mucilage, of gum tragacanth, and the oil. There are numerous other forms of emulsions recommended, as well as combinations with medicinal syrups, and cod-liver oil creams, jellies, and bread; and various devices are familiarly employed as in the administration of unpleasant medicines. Failing all these, cod-liver oil has been introduced into the system by injection.
[640 words — estimated reading time: 4 minutes]