108 PHILOSOPHY OF ZOOLOGY. 



1 . Periosteum. This bears the same relation to the bone 

 as the skin to the body, serving as a covering for its surface, 

 and a sheath for the different cavities which enter it. It 

 varies in thickness, according to the nature of the bone. Its 

 texture is obviously fibrous ; and it possesses bloodvessels. 

 Its sensibility indicates the existence of nerves. Where 

 this organ covers cartilaginous processes, it is called Peri- 

 chondrium. 



2. Cariilaglivws basis. This part of bone apparently 

 consists of gelatine and coagulated albumen. The gelatine 

 may be obtained by boiling the bone, previously broken in- 

 to small fragments, for a considerable time in water. If the 

 liquor be sufficiently concentrated, it will gelatinize when 

 cold. The coagulated albumen may be obtained, by 

 removing the earthy salts by means of weak muriatic acid. 

 What remains is termed cartilage. It retains the original 

 figure of the bone ; and may be considered as the frame, in 

 the cells of which the earthy matter has been deposited. It 

 contains numerous bloodvessels, which reach it by passing 

 through the periosteum. 



2. Earthy Matter. The quantity of earthy matter may 

 be ascertained, by exposing the bones for some time to a red 

 heat. The cartilaginous basis is consumed, and the earthy 

 matter is left behind ; or the earthy matter may be obtain- 

 ed in solution, by steeping the bone in diluted muriatic 

 acid. It chiefly consists of lime united with phosphoric acid, 

 forming phosphate of lime. Carbonate of lime occurs, but 

 generally in small quantity. Phosphate of magnesia is like- 

 wise found, sometimes to the amount of 3 per cent. HAT- 

 CHETT detected a minute portion of sulphate of lime ; and 

 BERZELIUS has confirmed the observation of other experi- 

 mentalists, as to the occurrence of fluate of lime to the extent 

 of 3 per cent. 



4. Fat. This part of bones bears a close resemblance 

 to the fixed oils. In some bones, ay those of whales, it oc- 



