Isinglass

Isinglass (supposed to be derived from the German Hausenblase, 'bladder of the sturgeon'), the Ichthyocolla (ichthys, 'a fish'; kolla, 'glue') of the classical and scientific writers, was formerly obtained only from the common sturgeon (Accipenser sturio), and consisted of the dried air-bladder of the animal. The necessities of modern commerce have, however, led to the discovery that the same part in many other fishes forms good isinglass; and instead of Russia, as formerly, being almost the only producing country, large quantities are now brought to Britain from South America (chiefly from Maranham), some from the East Indies, New York, and Canada. The commercial varieties of this material are numerous; and besides them others are occasionally met with, as the Manilla, in thin cakes; the Para, which is the most remarkable of all, resembling grapes of a reddish-brown colour, growing from a straight thick stem, being the dried ova of the Sudis gigas, a large fish common in the mouths of the Amazon. An inferior kind is also made of cod-sounds and sole-skins, sufficiently good, however, to be used in fining beer and other liquids. Isinglass, strictly speaking, is not Gelatine (q.v.), but a good gelatine-yielding tissue, its value being enhanced by the ease with which it is abstracted from the membrane when compared with the complicated process necessary for separating and purifying the gelatine from the skins, &c. of other animals. When separated, however, the substances are identical in composition, and, if pure, are undistinguishable from each other.