It is questionable how far these adulterations may be detected by the operation of the oil, since the principles of its immediate action in various diseases is far from having been satisfactorily ascertained. Its nutrient properties are known, and must be admitted in common with all adipose substances, and a knowledge of their constituents and action upon the human frame; but beyond this, namely, the specific qualities as adapted to counteract scrophula, rickets, rheumatic or gouty inflammation, neuralgia, pulmonary disorders, &c. is unknown. The well-ascertained effects of iodine in the relief of scrophulous diseases point out that substance as the immediate agent affording relief in those cases, but it has been ascertained that the quantity of iodine in the cod-liver oil is exceedingly small, being much beneath that which is ordinarily given in the treatment of scrophulous disorders, and without effect in those cases; still this small quantity may perhaps by nature be so incorporated in the composition of the oil, that although of diminished proportions, it may yet possess an increased power of action, as in the case of natural mineral waters. It may probably be truly averred, that no fictitious mineral waters, however admirably prepared, and however accurately constituted, according to the proportions of the several ingredients as ascertained by chemical analysis, are capable of producing the same effects as those by the water derived from the original spring. This may perhaps be the result of some electric or galvanic agency operating in its constitution, the place of which cannot be supplied by any substitute to be found in the laboratory of the chemist. Nature here manifests her decided superiority to the efforts of art, though ably directed by the hand of science. Dr. Pereira has suggested bromine to be the active principle in the oil, and others have attributed its efficiency to various phosphoric compounds. Dr. Williams refers its agency to some biliary principle; in short, nothing certain is known upon the subject: the cause may here be said to be occult, but the effect is apparent. Mons. Bretonneau asserts that he has obtained effects just as markedly beneficial to result from the use of the common whale oil, as from the cod-liver oil, although we know the power to be but very partially obtained from the liver of the cetaceous tribe.