CHABACTEKISTICS OF ANIMALS 



31 



inorganic matter, but differs from 

 them in containing more of the 

 mineral elements. The organic 

 matter constitutes about one-third 

 the total amount in mature bones, 

 and when freed from the inorganic 

 substances is known as ossein, a 

 form of gelatin. This may be 

 demonstrated by soaking a fresh 

 bone in weak hydrochloric acid 

 to dissolve out the inorganic 

 matter (decalcification) . All hard- 

 ening constituents are lost and 

 while the original shape of the 

 bone is retained, the mass is soft 

 and flexible like India rubber. 

 The organic matter gives bone its 

 elasticity and tenacity. The in- 

 organic or mineral matter con- 

 stitutes the other two-thirds and 

 is in the form of: 



Calcium phosphate . . . 

 Calcium carbonate . . . 

 Magnesium phosphate 

 Sodium salts 



57.35 per cent 

 3.85 per cent 

 2.05 per cent 

 3.45 per cent 



66.70 



The inorganic matter renders 

 bone hard and dense. This com- 

 bination of animal and mineral 

 substances gives solidity to the 

 bones, yet elasticity enough to 

 prevent fracture under ordinary 

 circumstances. It is very difficult 

 to break a green bone on this 

 account. 



On sectioning a bone there are 

 revealed two varieties of bone 

 texture: the outer or compact 

 tissue, and the inner, cancellated 

 or spongy tissue (Fig. 3). 



Fig. 3. — Sagittal section of right 

 large metatarsal bone of horae: 

 S.c, Compact substance; S.s., 

 spongy substance; Cm., medul- 

 lary cavity; F.n., nutrient fora- 

 men. Note the greater thick- 

 ness of the compact substance 

 of the anterior part of the shaft. 

 (Sisson, Anatomy of Domestio 

 Animals.) 



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