STRUCTURE OF BONE. 365 



insect. Nothing of this kind takes place among 

 the Vertebrata ; where all the organs are deve- 

 loped in regular and harmonious succession, 

 without the slightest mutual interference, and 

 without those vicissitudes of action and of tor- 

 pidity, which we witness in the chequered ex- 

 istence of the insect. 



2. Structure and Composition of the 

 Osseous Fabric. 



THE process employed for the formation and ex- 

 tension of the solid frame work of the Verte- 

 brata differs totally from that which we have 

 seen exemplified in the growth of shells, or of 

 the hard coverings of insects and of 'crustaceous 

 animals. These latter structures, and the modes 

 adopted for their increase, are suited only to 

 animals in which the functions of the economy 

 have not reached that perfection to which they 

 are carried in the higher classes. In the more 

 elaborate system of the vertebrata, the skeleton 

 is composed of true bones; that is, of solid pieces, 

 which, although they are dense calcareous struc- 

 tures, yet continue organized during the whole 

 period of developement, and form as much a 

 part of the living system as any other organ of 

 the body. We have formerly seen that the 



