ISINGLASS. A solid glutinous substance, almost wholly gelatine, chiefly from a fish of the sturgeon kind, caught in rivers of gary. The belluga yields the greatest quantity, as being the and moat plentiful fish in the rivers of Russia; but the sounds, or air bladders of all freshwater fish, yield, more or less, fine isinglass, particularly the smaller sorts, found in prodigious quantities in the Caspian Sea, and several hundred miles beyond Astracan, in the Wolga, Tail, Don, and even as far as Siberia. The following is the 4sual mode of preparing isinglass :—The sounds, or other parts of which it is to be made, are taken from the fish while sweet and fresh, slit open, washed from their slimy. Borden divested of every thin membrane which envelopes the sound, and then exposed, to stiffen a little in the air. In this state they are formed into rolls, about the thickness of a finger, and in length accor ding to the intended size of the staple: a thin membrane is generally selected for the centre of the roll, round which the rest are folded alternately, and about half an inch of each extremity of the roll is turned inwards. The due dimen sions being thus obtained, the two ends of what is called short staple are pinned together with a small wooden peg ; the middle of the roll is then premed a little downwards, which gives it the resemblance of a heartrsliape ; and thus it is laid on boards, or hung up in the air to dry. The sounds which compose the long staple are longer than the former; but the operator lengthens this sort at plea sure, by interfolding the ends of one or more pieces of the sound with each other. The extremities are fastened with a peg like the former, but the
middle part of the roll is bent more considerably downwards; and in order to preserve the shape of the three obtuse angles thus formed, a piece of round stick, about a quarter of an inch in diameter, is fastened in each angle with small wooden pegs, in the same manner as the ends. In this state it is permitted to dry long enough to retain its form, when the pegs and sticks are taken out, and the drying completed; lastly, the pieces of isinglass are collocated in rows, by packthread through the pegholes, for convenience of package and exportation. The common kinds of isinglass, called the "book" and "ordinary staple," are composed of the membranes, which will not admit of a similar for mation with the preceding; the pieces, therefore, after their sides are folded inwardly, are bent in the centre m such manner that the opposite sides resem ble the cover of a book, from whence its name : a peg being run across the middle, fastens the sides together, and thus it is dried the former. This sort is interleaved, and the pegs run across the ends, the better to prevent its unfolding. Ichthyocolla, or isinglass, is one of the purest and finest of the animal glues, of no particular smell or taste. Beaten into threads, it dissolves pretty readily in boiling water or milk, and forms a gelatinous substance, which yields a mild nutriment, and proves useful, medicinally, in some disorders.