COD-LIVER OIL (Oleum Morrhuae, or Oleum Jecoris Aselli), the oil obtained from the liver of the common cod (Gadus morrhua). The usual process is to heat the fresh, cleaned livers by steam to a temperature above that of boiling water, or, by more recent practice, to a lower temperature, the livers being kept as far as possible from contact with air. The oils so obtained are termed "steamed-liver oils." The "pale" and "light brown" oils are used in pharmacy; the "brown" oil, the cod oil of com merce, being obtained from putrid and decomposing livers, has an objectionable taste and odour and is largely employed by tanners. By boiling the livers at a somewhat high temperature, "unracked" cod oil is obtained, containing much "stearine," which separates on cooling and is sold as "fish stearine" for soap-making, or as "fish-tallow" for currying. The oil when freed from the stearine is known as "racked oil." "Coast cod oil" is the commercial name for oil obtained from the livers of various kinds of fish; e.g., hake, ling, haddock, etc. The chief centres of the cod-liver oil industry are Lofoten and Romsdal in Norway; the oil is also pre pared in the United States, Canada, Newfoundland, Iceland and Russia.
Cod-liver oil contains palmitin, stearin and other more complex glycerides; the "stearine" mentioned above, however, contains very little palmitin and stearin. Therapic and jecoleic acids have been identified and apparently do not occur elsewhere in the ani mal kingdom. Other constituents are cholesterol (0.46-1.32%), traces of calcium, magnesium, sodium, iodine, chlorine and bro mine, and various aliphatic amines which are really secondary products.
Cod-liver oil is very readily absorbed from the skin and exerts all its therapeutic actions when thus exhibited. This method is often used for infants or young children with abdominal or other forms of tuberculosis. When taken by the mouth it is easily assimilable. It may cause nausea at first, but usually tolerance is soon established.
Cod-liver oil may be given in all wasting diseases, in tubercu losis and in rickets. It is occasionally valuable in chronic rheuma toid arthritis. Care must be taken to avoid the nausea, loss of appetite and diarrhoea, easily induced by this oil. It may be given in capsules, or as an emulsion, with or without malt-extract. The value of cod-liver oil depends partly on the food value of the oil itself, partly on the fat-soluble vitamin (see VITAMINS) and iodine it contains.
Cod-liver oil is used extensively in poultry feeds, either unmixed or combined with other oils, as a growth-accelerator for young chicks. It has proved especially valuable when their exposure to sunlight is restricted, making it commercially practicable to raise chicks in poorly lighted structures.