Substitutes for cod-liver oil are sold : e.g. Pilchard Oil; Cotton Seed Oil with 6 per cent oleic acid; Lipanin, olive oil with 6 per cent oleic acid; and various cod-liver oil emulsions, containing one or more of the constituents, mucilage, alkali, glycerin, and malt extract. Pancreatic Emulsion is a mixture of emulsified lard, pigs' pancreas and oil of cloves.
Petroleum Emulsions are also sold. They merely act as lubricants, for petroleum is a hydrocarbon, not a fat, and is not absorbed.
A study of the composition of the various proprietary foods shows that some may be regarded as more or less pure foods, while others are combinations of fat and protein, fat and carbohydrate, protein and carbo-hydrate, or all three constituents.