46 CHEMICAL PHYSIOLOGY. 



insects and articulate animals (C 9 H 15 N0 6 ) dextrose 

 fermentescible sugar. 



Bones. The bones consist of a peculiar combination of 



organic matter with mineral earthy phosphates, 

 and contain as accessory matters marrow, blood- 

 vessels, and cellular nuclei in the cavities called bone- 

 corpuscles. 



osseine. The organic substratum is called osseine (a name 



which it would be better to apply to the entire bone 

 tissue), the mineral matters are termed bone-earth. 

 The osseine is obtained by extracting the bone-earth 

 with dilute hydrochloric acid. It retains the structure 

 of the bone substance, which is disposed in concentric 

 layers round a tubular centre. Osseine dissolves on 

 boiling in water like glutin, but differs from the latter 

 in several particulars, although the product of the 

 solution in hot water is true gelatine. Of osseine 

 purified bones contain from 29'5 to 30'9 per cent., with 

 which 68'3 to 69*4 per cent, of earthy salts are in com- 

 bination. The regularity of these proportions has led 

 to the assumption that bone is a chemical compound in 

 definite atomic proportions of osseine and earths, and 

 not merely a tissue in which earths are deposited. 

 Some remarkable experiments show that gelatine and 

 earthy phosphates have a peculiar attraction for each 

 other. Thus a mixture of gelatine and bone-earth in 

 hydrochloric acid, when neutralised by ammonia, 

 deposits bone-earth with 20 per cent, of gelatine ; 

 vice versa when tannic acid is added to such a solution 

 tannate of gelatine with much bone-earth is precipi- 

 tated. Bone-earth contains 9*1 per cent, of calcium 



