Ambergris is a grayish-white fatty substance which occurs in commerce in pieces of various sizes—those as large as a fist are rare—of a penetrating, decidedly disagreeable odor. It is soluble in alcohol, and when properly diluted the odor becomes pleasant and it is so permanent that a piece of linen moistened with it smells of it even after being washed with soap. By itself, ambergris is not much used; it finds its chief application in combination with other odors or as an addition to some perfumes in order to make them lasting. CASTOR. _Latin_—Castoreum; _French_—Castoreum; _German_—Castoreum. This is a secretion of the beaver (Castor fiber); it accumulates in two pear-shaped bags on the abdomen of the animal, both male and female. The hunters remove these bags from the body of the dead animal and in this form they are brought into commerce. These sacs are the length of a finger, at the thickest point the diameter of a thumb, and contain a greasy mass of yellowish-brown, reddish-brown, or blackish color, according to the nourishment of the animal. This mass constitutes castor; it has a strong, disagreeable odor, a bitter, balsamic taste, becomes soft when heated, is combustible, and almost entirely soluble in alcohol. It is probable that this secretion in its composition has some relation to the nourishment of the beavers which feed by preference on resinous vegetable substances. In commerce Canadian and Siberian castor are distinguished; the latter is more valuable and has almost disappeared from the market. It possesses a peculiar tarry, Russian-leather odor, probably due to a substance present in birch bark, upon which the Siberian animals feed almost exclusively. Canadian castor has an odor more nearly resembling pine resin. In perfumery castor is rarely used, usually only for fixing other odors. HYRACEUM. The substance occurring in commerce under this name, the excrement of an animal found in Capeland, the rock badger or rock rabbit (Hyrax capensis), is very similar in its properties to castor, and according to comparative experiments made by us can be used in place of the latter. MUSK. _Latin_—Moschus; _French_—Musc; _German_—Moschus. Of animal substances, musk is most frequently used in perfumery, and possesses the most agreeable odor of them all. Moreover, the odor of musk is the most intense that we know, actually imponderable quantities of it being sufficient to impart to a large body of air the strong odor of musk. This substance is derived from a deer which attains the size of a small goat and, like the chamois of the Alps, lives on the highest mountains of the Himalayas. Only the male animal (Moschus moschiferus) produces musk, which is secreted in a sac or rather gland near the sexual organ. Musk being subject to the worst adulterations owing to its high price, we append a description of the substance as well as of the sac or bag in which it appears in commerce.