ITS COMPOSITION IN DISEASES. 31 



deprived of nutriment by the intervention of healthy parts. Our 

 analyses yield, therefore, very nearly the same composition for 

 necrosed as for healthy bones ; the organic matter sometimes 

 appears to be rather augmented, although it is occasionally slightly 

 diminished ; they commonly present the same characters as strongly 

 macerated bones. 



Fossil bones have also been made the subject of numerous 

 investigations.* The locality from which they have been removed 

 should always be considered in these inquiries, for to this we must 

 obviously refer many of the modifications presented by their com- 

 position ; thus, for instance, the mass in which they are embedded 

 frequently exerts a chemical action upon them by decomposing or 

 metamorphosing the organic matter or the phosphate of lime, 

 whilst it also readily becomes infiltrated (especially its carbonate 

 and sulphate of lime) into the bone-canals. 



The quantity of organic matter contained in fossil bones varies 

 very considerably ; thus, for instance, in some cases the organic 

 matter contained in them has been found to be scarcely diminished 

 when compared with that of fresh bones, whilst on the other hand 

 many of these bones exhibit no remaining trace of organic matter. 

 We have already referred to the observation made by Bibra, that 

 the cartilage of fossil bones is generally converted into a substance 

 which at once yields glutin, after the mineral matters have been 

 thoroughly removed. It seems a priori more than probable that 

 the composition of the phosphate of lime might undergo a change 

 in fossil bones ; but still this salt has almost always been found to 

 consist of 8 CaO.3 PO 5 , which is the same composition as that 

 occurring in fresh bones. It is therefore very questionable whether 

 the occurrence of small crystals of apatite, 3 CaO.PO 5 , in fossil 

 bones, or in bones which have lain for a long period of time in the 

 earth (Girardin and Preisserf), can depend upon a metamorphosis 

 of the chemical constitution, or (as seems less improbable) on an 

 arrangement of the minute particles of phosphate of lime into 

 crystals. Carbonate of lime generally occurs in far larger quan- 

 tities in fossil than in recent bones, although this increase is 

 frequently only relative, in consequence of the organic substance 

 having disappeared from the bone; more commonly, however, 

 this carbonate of lime is absolutely augmented either by infiltration 

 from without, or in certain soils, from a portion of the phosphate 

 of lime being decomposed by carbonic acid or carbonates. Ma-- 



* On the literature of this subject, see Vol. 1, p. 425. 



t Ann. de Chim. et de Phys. 3 SeY. T. 9, p. 370-382, 



