14 COMPOSITION OF BONES. 



by fine tubes, for the passage of plasma through its sub- 

 stance ; but the red particles of the blood are excluded. 



True osteine and dentine are peculiar to the highest 

 division or province of the Animal Kingdom, which pro- 

 vince has been termed " Vertebrata," from the prevalent 

 disposition of the osseous matter in successive groups of 

 more or less confluent bones called " vertebrae." (From 

 verto^ I turn; these being the parts on which the body 

 bends or rotates.) 



Before entering upon the disposition of the bony mat- 

 ter, a few words may be premised as to the composition 

 of that matter in the different classes of vertebrata. These 

 classes are four : Fishes, Keptiles, Birds, and Mammals, 

 which latter class includes the hair-clad beasts, commonly 

 called quadrupeds, with the naked whales and human 

 kind. Fishes have the smallest proportion, birds the 

 largest proportion, of the earthy matter in their bones. 

 The animal part in all is chiefly a gelatinous substance. 



PROPOKTIONS OF EARTHY OR INORGANIC, AND OF ANIMAL OR ORGANIC, 

 MATTER IN THE BONES OF THE VERTEBRATE ANIMALS. 



100.00 100.00 100.00 100.00 



