CHEMISTRY OF THE BONES. 347 



THE ORGANIC MATTER OR OSSEIN. 



The crude organic substance in the bone is commonly 

 called ossein; it may be extracted with hot water and forms 

 a gelatinous mass on cooling. But fuller investigations show 

 that this ossein is not a single substance, as several different 

 constituents may be separated by proper solvents. These are, 

 however, closely related substances and for our present pur- 

 pose they may all be considered as practically identical with 

 the collagen or glue-forming substance of the connective tis- 

 sues. The conversion of the ossein or collagen into gelatin 

 appears to be a hydration process, as at a higher temperature 

 the reverse operation takes place. The preparation and prop- 

 erties of bone gelatin may be illustrated experimentally : 



Ex. Clean a long, slender bone (best, a rib), and immerse it in dilute 

 hydrochloric acid of about ten per cent strength. Let it remain several 

 days. At the end of this time remove the bone from the acid and observe 

 that it has lost its rigidity and has become very flexible. It may be even 

 possible to tie it in a knot. Wash the elastic mass several times in fresh 

 water to remove all the hydrochloric acid, then with a little dilute sodium 

 carbonate solution followed by more water, and finally boil it with a small 

 amount of pure water. By heating it long enough the ossein becomes 

 converted into gelatin, which solidifies, on cooling, to a jelly. 



By boiling the bone ossein under pressure the formation of the gelatin 

 is very much hastened. 



The solution as obtained above may be used for tests such as were 

 described in Chapter V, under Gelatin. 



THE MINERAL MATTER IN BONES. 



We are not able to say exactly how the mineral elements 

 are combined in the moist fresh bone. Our knowledge of 

 these combinations is practically limited to what we can learn 

 by a study of the residue left on burning the bone completely, 

 known as boneash. This is a white powder containing the 

 non-volatile compounds, of which calcium phosphate is the 

 most important. The following table shows the average com- 

 position of human boneash : 



