CHEMICAL COMPOSITION OF BONE. 259 



action of llic fire. If it be now examined, it will be found 

 to have lost nearly half its original weight, and to have be- 

 come exceedingly brittle; this, as already mentioned, being 

 the natural ])roperty of phosphate of lime, when deprived of 

 its animal cement. We may perceive on the surface of a 

 bone so treated, a number of minute crevices, showinc: where 

 this animal substance had been situated, in its original state. 

 On breaking the bone across, we may also discover the size 

 and shape of the cavities which contained the marrow, or 

 oily fluid above mentioned. 



It is easy to reverse this process by steeping the bone in 

 an acid sufficiently diluted to prevent its injuring the animal 

 membrane, but yet sufficiently powerful to dissolve the 

 phosphate and carbonate of lime. Diluted nitric or muria- 

 tic acids may be used for this purpose, and will, in this way, 

 gradually separate the earthy particles from the membranous 

 portion of the bone. During the action of the acid a few 

 bubbles of carbonic acid gas make their appearance, indi- 

 cating the presence of a small quantity of carbonate of lime, 

 which always exists in bones, intermixed with the phos- 

 phate. The phosphate may be recovered from its solution 

 in the acid by precipitation with a pure alkali, such as a so- 

 lution of ammonia. This precipitate is readil}' dissolved, 

 without effiirvescence, by nitric, muriatic, or acetic acids. 

 A small quantity of sulphuric acid may also be detected in 

 the fluid by the addition of nitrate of barytes. Iron, in 

 small quantity, is also found in the composition of human 

 bones. 



The substance which remains, after the earth has been 

 thus abstracted, retains the exact figure and dimensions of 

 the original bone, but has lost all its other mechanical pro- 

 perties. It is soft, flexible, and elastic; resembling in every 

 respect the muscular or fibrous structures, and being, like 

 them, resolvable into gelatin and albumen by long boiling 

 in water. This substance has sometimes, but erroneously, 

 been considered as identical with cartilage; for it has nei- 

 ther the whiteness, nor the elasticity, nor the texture of carti- 

 lage, nor is it at all similar to that substance in its chemical 



