Production of Isinglass on the Coasts of India. 79 



healthy animal fluids, it is obtained in large proportion from skins, 

 most of the white and soft parts of animals, as cartilage, tendon, and 

 membrane ; also from bone and horns. It is likewise found in a 

 large proportion in cartilaginous fishes, and forms the natural ce- 

 ment of many shells. From all these gelatine may be extracted 

 by simple boiling in water, with different precautions in regard to 

 cleaning. From bones it may be obtained by the same process, but 

 with the assistance of pressure, and still more easily, if they have 

 been first acted on by muriatic acid, to remove the phosphate of 

 lime. The obtaining of gelatine may thus give rise to a number of 

 employments, which may be practised wherever these offals are 

 obtainable, and the product, in the form of gelatine, can be turned 

 to account. 



The solution of gelatine, which, on cooling, becomes a tremulous 

 mass, may by further evaporation be converted into a hard and brit- 

 tle substance, well known by the name of glue. This is made from 

 the parings of hides or horns of any kinds, the pelts obtained from 

 furriers, the hoofs and ears of horses, oxen, calves, sheep, &c. In 

 France it is made from the raspings and trimmings of ivory, the 

 refuse pieces and shavings left by button-mould makers, and from 

 other kinds of hard bone. Size, again, is made by boiling down in 

 water the clippings of parchment, glove-leather, fish-skin, and other 

 kinds of skin and membrane. This is used either alone or mixed 

 with flour paste, gum arabic, or tragacanth, and employed by book- 

 binders, paper-hangers, and painters in distemper. 



Mr. Hatchett, many years since ascertained that the viscidity and 

 tenacity of the varieties of gelatine are qualities inherent in each, 

 depending in one, on the age of the animal, the old giving a much 

 stronger glue than the young ; in another, on the substances by 

 which it is furnished, as glue obtained from the skin is much stronger 

 than the solid gelatine from bones, sinews, or any other part. Mr. 

 H. further found the force of adhesion of the glue from skin was 

 generally proportionate to the toughness of the skin, those which 

 were soft and flexible yielding a thinner gelatine than the hard bony 

 skins, at the same time that they yielded it more easily. 



Considering the nature and sources of Gelatine, and the high 

 price of Isinglass, it is not surprising that the former should be fre- 



