COMPOSITION OP BONES. 



113 



[ 236. The internal skeleton of the vertebrate is formed, 

 for the most part, of bone, a substance which is peculiar 

 to this primary division of the animal kingdom. It consists 

 of an organic gelatinous matter, hardened by inorganic earthy 

 particles distributed regularly throughout the animal tissue. 

 The relative proportion of the organic to the inorganic matter 

 varies in the different classes of thevertebrata; thebones of fishes 

 have the least, those of birds the greatest proportion of inorganic 

 elements, whilst reptiles and mammals occupy an intermediate 

 position ; the mammals, however, especially the active preda- 

 cious genera, having a larger proportion than the reptiles. From 

 a series of experiments recently made, and conducted with 

 great care, by Bibra,* on thoroughly dried bones of fishes, rep- 

 tiles, birds, and mammals, the following results were obtained. 



[ 237. PISHES. 



* Chemische Untersuchungen iiber die Knochen u. Zahne des Mens- 

 chen u. der Wirbelthiere, 1844. 



t Fiom the femur. i 



