minimal Substances. 287 



9. Sulphur. 12. Alkalies. 



10. Phosphorus. 13. Earths. 



11. Acids. 14-. Metals. 



1. Gelatine, it has already been intimated, 

 constitutes the principal part of the cutis, or 

 skin, of animals. It is, however, found in other 

 parts. The well-known culinary process of 

 making jelly from calves' feet, and from the skin 

 of a kind of sturgeon, called isinglass, produces 

 nt once the substance called in chemistry gela- 

 tine. If the calves'- feet jelly were evaporated 

 to dryness it would be glue, and indeed glue is 

 produced by boiling down pieces of the skin of 

 animals, generally those parts which are cut off 

 by the tanners and skinners : gelatine and glue 

 are, therefore, the same. It exists more or less 

 not only in the solid but in the fluid parts of 

 animals : blood and milk always yield it, and it 

 exists even in the bones, horns, and hair. It is 

 a nourishing article of food, and constitutes the 

 basis of soups. Gelatine consists properly of 

 carbon, hydrogen, nitrogen ? and oxygen. Phos- 

 phat of lime and soda are found in it, but are 

 probably only held in solution by it. 



2. Albumen is the white of the egg, in which, 

 howev-er, it is combined with sulphur, and soda. 

 It is also the chief constituent of the serum of 

 blood. When heated to the temperature of 

 165, it coagulates into a white solid mass of 

 precisely the same weight. It is also coagulated 

 by acids and alcohol. When dried, it becomes 



