been taken of these fish during a season. Menhaden oil is rarely if ever used for edible purposes. It is used principally in the leather trade and sometimes in the adulteration of cod liver oil made in Newfoundland.
Sardine Oil.—Sardine oil is principally prepared in Japan from the Japan sardine (Clupea sardinus). It is not used to any extent for edible purposes. It is also prepared to some extent in the boiling of sardines in France preparatory to packing in oil.
Salmon Oil.—This oil is obtained in large quantities on the Pacific coast. It is one of the fish oils which has an agreeable odor and taste and, therefore, can be used for edible purposes. It has a specific gravity at 15 degrees of about .926 and its iodin number is about 160.
Cod Liver Oil.—The most important of all the animal oils for food purposes is the oil which is obtained from the liver of the cod (Gadus callarias). Cod liver oil is valuable for food purposes not on account of its odor and taste, which are usually quite disagreeable, but by reason of the specific effect which it is often said to exercise in cases of emaciation and general disorder of the functional activities of the body. It is a food or medicine, whichever it may be best called, which is highly prized in tuberculosis and similar diseases. The oil is chiefly prepared in the Loffoden Islands. Different classes of oil are prepared which are differentiated chiefly by their color, the lighter the color the higher the quality of the oil. The chemical composition of cod liver oil is extremely complex, many different kinds of substances having been found in it by various authorities. The probability is that many of these supposed substances are only mixtures of others. Yet it cannot be denied that the number of chemical compounds occurring in cod liver oil is very much greater than that which occurs in ordinary oils. Both the medicinal and food values of the oil are often attributed to these bodies which occur in minute quantities.
Properties.—Cod liver oil at 15 degrees has a specific gravity of .922. Its iodin number varies very greatly but is always high, ranging from 150 to 180. Its refractive index is also very high, namely 1.47.
An important constituent of cod liver oil is cholesterol. Cod liver oil contains naturally a small quantity of iodin and this natural compound of iodin is one of the properties to which much of its medicinal virtue has been attributed. The quantity present is extremely minute, and probably never exceeds .002 of one percent.
Adulteration of Cod Liver Oil.—Owing to its increasing price cod liver oil has been subjected to many forms of adulteration. The chief adulteration consists in the admixture of fish liver oil of lower quality or the use of blubber oil. Seal and whale oils have been used very extensively in the adulteration of cod liver oil. Japan fish oil and, in fact, all other fish oils which are of a character not to disguise the properties of cod liver oil have been used.
