This is a fixed oil, obtained from the fresh livers of Gadus morrhua, and of other species of Gadus. It contains faint traces of iodine and bromine and sometimes of phosphorus. It also contains a vitamine, for when given with polished rice it prevents beri-beri (Funk), and when substituted in equal caloric value for lard in a standard diet for rats it induced growth which had failed from the lard (Osborne and Mendel). According to Leathes it is a fat with a high percentage of unsaturated fatty acids, so that when taken as food it saves the liver its usual work of desaturation. The cheap oil obtained from putrefactive livers contains various bases, such as choline and tyramine. A watery extract of such has a vasoconstrictor action. Such oils are no longer used.

Cod-liver oil has a fishy odor and a bland, fishy taste, which are, at least in part, due to the presence of free fatty acids. These are abundant in the cheaper oils, and in the good oils are more readily produced in hot weather. As the fishy taste makes cod-liver oil especially nauseating to many it is customary to administer the oil in admixture with the extract of malt, or in the form of a sweetened and flavored emulsion. It has been shown experimentally that emulsified oils are more readily absorbable than the unemulsified, especially by persons of poor nutrition, and it is noted clinically that the emulsion is easier to take and is better borne by the stomach than the pure oil. It should be given after meals as an addition to the regular food, or two or three hours after meals, to permit of ready digestion in the duodenum. It should not be given just before meals.

Therapeutics

The great value of cod-liver oil is as a nutrient in states of poor nutrition and poor resistance, hence its use in tuberculosis, chronic bronchitis, and chronic susceptibility to colds. It is also of use in spasmophilia and rickets. In a negro district in New York, Hess showed that rickets could be prevented by giving cod-liver oil at an early age. Cod-liver oil is sometimes employed by inunction in cases of severe malnutrition, but the usefulness of this procedure is seriously questioned. On subcutaneous injection Mills and Congdon (1911) found that pure oils were slowly absorbed by starving animals, and more rapidly absorbed when made into an emulsion with 3 to 5 per cent. of lecithin. It is probable that such an emulsion would be partly absorbed on rectal administration.

Preparations And Doses

Cod-liver oil - 2 drams (8 c.c).

Emulsion, 50 per cent. of oil, made with acacia and flavored with sugar and wintergreen - 4 drams (15 c.c).