Not officinal. - The purified fat of sheep's wool. It is also found in other tissues containing keratin.

Characters. - Pure lanolin is of a consistence between resin and fat, but it rapidly takes up 100 per cent. of water. It is yellowish-brown, becoming darker on exposure, and has a faint smell.

Reactions. - It is a very stable compound, remaining unchanged after boiling with alkalis. When dissolved in anhydrous acetic acid and a small quantity of strong sulphuric acid added, a rose colour is developed, rapidly becoming dark blue and then green.1

Impurities. - It ought not to contain more than 0.1 to 0.5 per cent. of free fatty acid, since the presence of a greater amount, especially of the lower fatty acids, is likely to produce irritation of the skin.

Composition. - Lanolin is a cholesterin-fat, having choles-terin, instead of glycerin, combined with the fatty acid.

Uses. - Lanolin is recommended by O. Liebreich as a basis for ointments, and as more valuable than glycerin- or petroleum-fats (vaselin), because of its unirritating qualities when pure, but chiefly from its great absorbability when rubbed into the skin. This property is perhaps connected with the fact that lanolin, in the animal kingdom, is closely associated with keratin 1 Oscar Liebreich, 'Ueber das Lanolin, eine neue Salbengrundlage,' Berlin, klin. Wochens., 1885, No. 47.

forming cells. Ointments containing carbolic acid and corrosive sublimate rapidly produce the physiological effects of the drug, when rubbed into the skin.

Lanolin has been found useful in the pruritus of old people and in seborrhoea sicca and other skin diseases, but its chief use is in the application of drugs to the skin by means of ointments.1 An ointment with iodide of potassium is useful in relieving the swelling and pain of chronic joint-affections.