334 THE TISSUES. 



total amount of the earthy matters in bone remains constantly the 

 same. The herbivora have more carbonate of lime in their bones 

 than the carnivora, and the pachydermata and cetacea most of all. 



The bones of fishes contain the least earthy matter of all (21 to 

 57 per cent.). 



The varying amount of phosphate of lime in the different bones 

 has already been stated (p. 54). The bones of birds contain more 

 of it than those of mammals, it sometimes rising to 84.3 per cent. 

 Carnivorous birds, however, have but little more than mammals. 



In pregnancy, the consumption of phosphate of lime is so great 

 in the development of the skeleton of the foetus, that sometimes 

 scarcely any traces of it can be found in the urine of the mother ; 

 and fractures now occurring, unite with extreme difficulty, and 

 sometimes, indeed, not at all. The softened condition of the bones 

 constituting rickets also most frequently occurs during dentition, 

 while the phosphate of lime is required for the development of the 

 teeth, the latter not being affected by this disease. 



It is a singular fact that the cranial bones exhumed at Pompeii 

 contained more fluoride of calcium than the bones of the present 

 generation. 



Doubtless the food must exert some influence on the composition 

 of the bones. Softening of the bones occurred in chickens de- 

 prived, by Chossat, of the phosphate of lime. 



There is no appreciable difference in composition of the bones 

 of the male and the female. 



Alumina, oxide of iron, and' silica, are frequently found in fossil 

 bones; their presence being probably due to infiltration. 



In diseased bones, a great diversity of chemical composition is 

 found. The mineral substances are, however, almost always ab- 

 stracted from the osseous tissue earlier and in larger quantity 

 ( Von Bibrd) ; so that a relative increase of the osteine is observed. 

 Of the earthy matters, the phosphate of lime is the first to be re- 

 moved, and the last to be re-deposited after the cessation of dis- 

 ease. 



The osteine is very rarely affected in diseased bones. From some 

 cases of rachitis, however, both Marchand and Lehman n failed to 

 obtain any true glutin. 



The carbonate of lime frequently exceeds its normal amount, only 

 in osteophyte and new formations of bone. It appears usually to 

 diminish and afterwards to increase, with the phosphate. 



In primary sclerosis (eburnation), there is no excess of earthy mat- 

 ters in proportion to the osteine ; but a considerable augmentation 

 of the carbonate of lime in proportion to the phosphate. 



