RUSSIA Besides these now well-known commercial varieties, 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 color, growing from a straight thick stem; these are 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 tised in fining beer and other liquids.
One of the. qualities of gelatine is its power to form chemical combinations with cer tain organic matters; hence, when it is mixed and dissolved in a fluid containing such matters, it combines, and the compound is precipitated. It would appear that this com bination, however, is thread-like in its arrangement, and that the crossing threads form a tine net-work through the fluid, which, in falling, carries down all floating substances, which, by their presence, render the liquid cloudy; hence its great value in clarifying beer and other liquids. For this reason isingtass, which haS been found the best gela tine for the purpose, is very largely consumed by brewers.' • Isinglass, strictly speaking, is not gelatine, but its only value is from the excessive proportion of gelatine held in the tissues of the organ wikich yields it, greatly 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 Wits, etc., of other animals. When separated, however, the substances are identical iu coin position, , and, if pure, are undistinguishable froth each other.
Besides.the substances mentioned as yielding gelatine, formerly hartshorn shavings were used, and ivory turnings and saw-dust are still employed, both, however, chiefly for dietetic purposes for invalids; and various kinds of animal food are valued for the abundance of gelatine they contain, as the trepang and beche de mer (species of holothuria), sharks' tins, fish-maws, ray-skins, elephant hide, rhinoceros hide, and the softer parts, all of which are luxUries amongst the Chinese, Japanese, Siamese, .Malays, etc. Turtle-shells, Or the upper and lower parts of the shield (carapace and plastron),' constitute the callipash and callipee of the epicure, and form, in the hands of the expe rienced cook, a rich gelatinous soup. The fleshy parts of the turtle, calves' head and
feet, and many other things, might be enumerated as valuable, chiefly in consequence of their richness in this material.
CrLuE differs only from gelatins in the care taken in its manufacture, and in the selection of the materials from which it is made; almost every animal substance will yield it, hence all kinds of animal refuse find their way to the glue-makers' boilers. Nevertheless, the impossibility of preserving, for any length of time, the materials required for this manufacture, renders it necessary to adopt some system in choosing and preserving them, until sufficient quantities are collected, without fermentation or decom position. Hence the refuse of tanneries, consisting of the clippings of hides, hoofs, ear and tail pieces of ox, calf, and sheep, are preferred, because they can be dressed with lime, which removes the hair, and acts as an antiseptic. For this purpose they are placed in tanks with quicklime and water for two or three weeks, during which the lime is several times renewed, and the pieces frequently turned over. They are afterwards washed and dried, and are ready for use by the glue-maker, who usually gives them another slight lime-dressing, and subsequently washes them; they are afterwards exposed to the action of the air for a time, to neutralize the caustic lime. When well-drained, the piece3 are placed in flat-bottomed copper-boilers, which have a perforated false bottom placed a little distance above the true one, to prevent the burning of the mate rials, and which have been supplied with rain or other soft water up to two thirds the depth of the boiler, the pieces being piled up to sonic height above the top of the open i boiler. The whole is kept at a gentle boiling heat'until all the gelatinous part has dis solved out, and the mass of material has sunk down into the fluid. The boiling is sus tained until, by repeated trials of small quantities, the operator knows the fluid is of the, right consistency, when it is drawn off carefully into the congealing boxes, and fresh materials are added to the residue left behind in the boiler, and the process is repeated.