50 VETERINARY PHYSIOLOGY 



the large amount of inorganic matter, chiefly calcium phosphate, 

 and the nature of the organic matter — collagen. 



(3) Metabolism. — Although bone consists so largely of 

 inorganic matter it is permeated by blood-vessels and living 

 cells, and it undergoes metabolic changes not only during 

 development but in the full grown animal. In fasting and 

 in the conditions of acidosis (p. 481) the lime salts may 

 be removed from the bone to the blood and excreted. In 

 rickets the metabolism of growing bone is modified, the lime 

 salts not being properly laid down or being too rapidly 

 removed ; possibly both these changes go on together. The 

 bones are thus softened and undergo deformity. In osteo- 

 malacia there is a softening of the bones due to the 

 removal of lime salts. 



