GELATINE. 229 



spontaneously, and then collecting and pressing the 

 curd thus formed. The color of cheese is very com- 

 monly heightened by the use of annotto, or some 

 other yellow dyestufF. In using these substances, 

 care should always be taken to use only pure mate- 

 rials. 



589. Gelatine, the fourth great principle of ani- 

 mal matter, is a tough, colorless substance ; in cold 

 water, it very slowly softens and dissolves ; in boil- 

 ing water, it dissolves more readily, and forms a so- 

 lution, which becomes a jelly as it cools. The skin, 

 horns, and hoofs of animals, consist principally of 

 hard, dry gelatine ; and it likewise occurs in many of 

 the softer parts of the body, associated with albumen. 



690. Common glue and isinglass consist almost 

 wholly of gelatine ; the former is prepared by boil- 

 ing the clippings of skin, refuse horns, hoofs, and 

 similar matters, in water ; a strong solution of gela- 

 tine is thus obtained, which, as it cools, becomes a 

 jelly, and is then termed, size ; this, when cut in 

 slices, and dried in the air, is the glue of the shops. 



591. Isinglass is the lining membrane of the swim- 

 ming bladder of the sturgeon ; but inferior sorts of 

 isinglass are obtained from other fishes. Gelatine 

 is insoluble in spirit. In the dry state, it may be 

 preserved unchanged, for any length of time ; but 

 when moist, or dissolved in water, it very soon begins 

 to change ; it becomes mouldy, and putrefies. Gela- 

 tine consists of — 

 20 



