We proceed now to report the results of our examinations of these communications, and of the investigations to which the enquiry has led.
Cod-liver oil has long been the object of a considerable commerce arising principally from the decided superiority which it possesses over other animal oils, for the preparation of chamois leather; but it has only been within about twenty years that it has been used in medicine. It was first employed as a remedy for rheumatic pains, then for bronchial affections, and subsequently as a remedy for scrofula and consumption. It now constitutes one of the medicinal agents most extensively used, and one of those, on the action of which medical men place the greatest reliance, as a remedy capable either of curing very formidable diseases, or of retarding their fatal termination.
The most important memoir which has been published on cod-liver oil is that of Dr. Jongh, in which three kinds of oil are described as met with in commerce, which are called the black, the brown, and the white cod-liver oil. These oils are represented to consist, principally, of oleic and margaric acids, and glycerine, and, as accessory bodies, of butyric acid, acetic {122} acid; some principles appertaining to the bile, a non-azotised yellow or brown coloring matter, called gaduine, iodine, phosphorus, and some inorganic salts. In France, Messrs. Girardin and Preisser have been engaged in comparing the effects of the oil obtained from the cod with that obtained from the ray; and they advocate the superiority of the latter for medicinal use. But this superiority seems to depend, in part, on the circumstance, that the oil obtained from the livers of the ray, being carefully prepared by the pharmaciens, and being transparent, and of a light yellow color, proves less offensive to the patients than the cod-liver oil of commerce, which is generally thick, of a dark color, and has a disagreeable flavor. This, however, is scarcely admitted at the present time. Moreover, it appears from recent observations, that the above characters cannot be much depended upon for distinguishing the two kinds of oil, in consequence of their being so variable.
According to Messrs. Girardin and Preisser, these two oils contain iodine in the state of iodide of potassium, and in quantity much less than had been indicated by Dr. Jongh. The latter author gives, as follows, the quantity of iodine in 1,000 parts of oil:—
| Black cod-liver oil | 0,295 parts of iodine. |
| Brown cod-liver oil | 0,406 parts of iodine. |
| White cod-liver oil | 0,374 parts of iodine. |
Messrs. Girardin and Preisser have found in a litre (thirty-five fluid ounces),
| Of ray-liver oil | 0,180 gramme of iodine. |
| Of cod-liver oil | 0,150 gramme of iodine. |
According to M. Gobley, a litre of ray-liver oil, prepared by direct action of the fire, contains twenty-five centigrammes of iodide of potassium. M. Goodley was unable to find phosphorus in this oil.
Such were the principal analytical results known when M. Personne presented his memoir to the Academy. The uncertainty which appeared to attach to the subject, and the {123} variations in the statements of chemists, induced him to put to himself the following questions:—
1st. Do the oils of cod and ray-liver contain iodide of potassium or iodine?