STItUCTUKE OF BONE. 3'29 



destruction of the animal membrane. The oil con- 

 tained in the cavities exudes, and, taking fire, is 

 soon totally consumed. The bone then recovers 

 its whiteness, and undergoes no further change by 

 the action of the tire. If it be now examined, it 

 will be found to have lost nearly half its original 

 weight, and to have become exceedingly brittle ; 

 this, as already mentioned, being the natural pro- 

 perty 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, 

 showing 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 muriatic acids may be 

 used for this purpose ; and they 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, indicating 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 solution of ammonia. This pre- 

 cipitate is readily dissolved, without effervescence, 

 by nitric, muriatic, or acetic acids. A small quan- 

 tity of sulphuric acid may also be detected in the 



