GELATIGENOITS TISSUES Aso GELATINE. The gelatigenous tissues are substances resembling the proteine-bodies (albumen, fibrine, and caseine) in containing carbon, hydrogen, nitrogen, oxygen, and sulphur; but differing from them in containing more nitrogen and less carbon and sulphur. They consist of two principal varieties, viz., those which yield gluten (or ordinary g,'atine) and those which yield chondrine.
Gluten is obtained by more or less prolonged boiling with water, from the organic matter of bone (the osseine of Fremy), from tendons, skin, cellular tissue, white fibrous tissue, the air-bladder and scales of fishes, calves' feet, hartshorn, etc.; while chondrine is similarly obtained from the permanent cartilages, from bone-cartilage before ossifica tion, from enchondromatous tumors, etc.
Neither gluten nor chondrine appears to exist as such in the animal body, but is in all cases the result of the prolonged action of boiling water on the above-named tissues. Fremy's analyses (see his Recherches Chimiques sur les Os, in the Ann. de China. et de Phys., 1855, vol. xliii., p. 51) show that osseine is isomeric with the gluten which it yields, and further, that the amount of gluten is precisely the same as that of the osseine which yields it.
The following table exhibits the composition of osseine and the gluten yielded by it as determined by Fremy, and that of chondrine as determined by Mulder: Osseine. Gluten. Chondline.
Carbon. . . 49.21 50.40 49.97 Hydrogen. 6.50 6.50 6.63 Nitrogen 17.86 17.50 14.14 Oxygen with a little sulphur . . ... 25.14 26.00 28.97 Gluten, when perfectly pure and dry, is a tough, translucent, nearly colorless sub stance. devoid of odor and taste. It swells when placed in cold water, and loses its translucency; but iti boiling water it dissolves, and forms a viscid fluid. which on cool ing forms a jelly. A watery solution containing only 1 per cent of gluten, gelatinizes on cooling. This property is destroyed both by very prolonged boiling and by the action of concentrated acetic acid. Gluten is insoluble in alcohol and in ether.
A solution of gluten is abundantly precipitated by solutions of corrosive sublimate and of bichloride of platinum, as well as by infusion of galls, of which the aetive prin ciple is tannin or tannic acid (the terms being synonymous). Tannic acid produces, even in very dilute solutions, a copious yellow or buff-colored precipitate of tanuate of gluten. The gelatigenous tissues unite in a similar manner with tannin; they extract it from its watery solutions, and form compounds with it which resist the action of putre faction. It is thus that hides are converted into leather (q.v.). The tests which we
have mentioned also precipitate albumen, but gluten may be distinguished from albumen by its not being thrown down (as is the ease with albumen) by the addition of ferro cyanide of potassium together with a little acetic acid. The gelatinizing property also serves to distinguish gluten When it amounts to 1 per cent or more of the solution.
On exposure to the atmosphere, gluten becomes more rapidly putrid than•almost'any other animal substance., Under the influence of oxidizing agents, it yields the same products as the proteine-bodies; treated with the mineral acids or with alkalies, it yields glycocine (q.v.)—known also as glycine, glycocoll, and sugar of gelatine—leucine (q.v.), and other products.
Isinglass, which is prepared from the air-bladder of the sturgeon, etc., when boiled with water, furnishes gluten in a nearly pure state. Glue and size are two well-known forms of impure gluten or•gelatine.
Ch,oncirtne resembles gluten in its physical properties, and especially in its property of gelatinizing. It differs, however, slightly from it in chemical composition (see the above table), and in its behavior towards reagents. For instance, acetic acid, alum, and the ordinary metallic salts of silver, copper, lead, etc., which produce no apparent effect on a solution of gluten, throw down a precipitate from a solution of chondrine; while, on the other baud, corrosive sublimate, which precipitates gluten freely, merely induces a turbidity in a solution of choudrine.
We do not know much regarding the physiological relations of these substances.. Gluten (according to Scherer) usually exists in the juice of the spleen, but in no other part of the healthy animal body; it is sometimes found in the blood in cases of leueocy thtemia, in pus, and in the expressed juice of cancerous tumors. Chondrine has been found in pus. The gelatigenous tissues rank low in, the scale of organization, and their uses are almost entirely of a physical character. Thus they form strong points of con nection for muscles (the tendons), they moderate shocks by their elasticity (the cart's' lages), they protect the body from rapid changes of temperature by their bad conducting power (the skin), and they are of service through their transparency (the cornea).