Castor is much adulterated--pebbles, pieces of lead, dried blood, etc., being frequently found in the sacs. These frauds can generally be detected in cutting the sac open. Spurious sacs are said to be frequently found among the genuine sacs of Canadian castor. These spurious sacs are prepared by drying a mixture of castor, resin, dragons' blood, etc., in the scrotum of goats. In perfumery, castor is now very seldom used, the perfumers preferring musk and civet, which, certainly, give a somewhat different scent. _Ambergris_ is a fatty, waxy substance, often found floating on the sea on the coasts of Arabia, Madagascar, Japan, etc. It is also found in the cæcum of the sperm whale (_Physetus macrocephalus, Schow_), and is supposed by some to be a morbid secretion in the urinary bladder. According to Mr. Beale, it merely consists of the indurated fæces of the animal, perhaps somewhat altered by disease. It has a gray-white color, often with a black streak and a slight agreeable odor, like that of benzoin, which becomes more pronounced on heating. When held for some time in the hand it becomes soft and flexible. It melts at the temperature of boiling water, and, when more strongly heated, volatilizes in the form of a white vapor, leaving but slight traces of ash behind. Its specific gravity is 0.8 to 0.9. It is insoluble in water, sparingly soluble in cold spirit of wine, and more readily so in hot spirit of wine, ether and volatile and fat oils. It is almost completely soluble in absolute alcohol. Though ambergris crumbles readily, it can only with difficulty be converted into coarse powder. With the finger it can be polished like hard soda-soap. The principal constituent of ambergris is ambrin or ambrein, a non-saponifiable fat, which, from a saturated alcoholic solution of ambergris, crystallizes, after standing for some time, in the form of verrucose, whitish or lustrous acicular crystals. According to John, ambergris consists of 85 per cent. ambrin, 12.5 per cent. sweet balsamic extract, further benzoic acid, sodium chloride, and 1.5 per cent. insoluble brown residue. When distilled with water, ambergris yields 13 per cent. of a volatile oil having an agreeable odor. A red-hot iron wire readily penetrates ambergris, and from the hole thus made flows an oily liquid of a strong and agreeable odor.