ACIPENSER HUSO. 



not necessary to effect this change in gelatine. When ex- 

 posed to a high temperature, gelatine first' whitens, then 

 shrivels, and is carbonized; tremulous gelatine melts before 

 it undergoes these changes. When tincture of galls or any 

 astringent vegetable solution is dropped into a solution of 

 gelatine, an insoluble precipitate takes place; this is tanno- 

 gelatine^ a compound of the gelatine and tannic acid ; and it 

 is this combination that produces leather. Gelatine, like 

 gum, renders oils miscible with water, forming emulsions. 



Alcohol and ether do not dissolve gelatine, but they sepa- 

 rate it from the water of its solution ; in a thin solution, how- 

 ever, neither alcohol nor ether produces any obvious change. 

 All the concentrated acids- decompose gelatine, but diluted 

 acids dissolve it unchanged. When chlorine gas is mixed 

 with a solution of gelatine, a white solid matter, in filaments, 

 is separated, which Bouillon la Grange has named oxygenized 

 gelatine, but the nature of this change is unknown. The 

 alkalies, assisted by heat, dissolve gelatine, but do not produce 

 soaps. None of the earthy salts, with the exception of those 

 of baryta, precipitate its solution ; phosphate of soda, how- 

 ever, causes a slight milkiness in it. Among the metallic 

 salts, nitrate of silver only precipitates the solution of pure 

 gelatine. 



According to the analysis of Gay-Lussac and Thenard, the 

 components of gelatine are, carbon 47.881, + oxygen 27.207, 

 + hydrogen 7.914, + nitrogen 16.998, = 100.000. Such are 

 the chemical characters of gelatine, but these differ in some 

 particulars, according to the nature of the substances which 

 yield it. 



Gelatine is a nutritious article of food, though probably less 

 so than fibrine and albumen. Notwithstanding it is readily 

 digestible, it is not always suited to the digestive powers of 

 many dyspeptics. 



Gelatine may be considered as the least perfect kind of 

 albuminous matter existing in animal bodies ; intermediate, as 

 it were, between the saccharine principles of plants and thor- 

 oughly developed albumen. Indeed, gelatine in animals may 

 be said to be the counterpart of the saccharine principle of 

 plants, it being easily distinguished from all other animal 

 substances by its ready convertibility into a sort of sugar, 

 by a process similar to that by which starch may be so con- 

 verted. 



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