OF THE BONES. 371 



The bones experience in their development, transforma- 

 tions so much the more remarkable, that the different states 

 through which they pass correspond to similar, but permanent 

 states, which are observed in animals. 



After being fluid, like all the other parts, they become, first, 

 soft, mucous, or gelatiniform; secondly, cartilaginous, and 

 some of them fibrous and cartilaginous; thirdly, osseous. 



The bones are mucous, transparent, and colourless, at a pe- 

 riod very close upon conception. They then grow by vege- 

 tation, and form a continuous whole which is subsequently 

 divided. 



The cartilaginous bones, or temporary cartilages, do not 

 make their appearance until the end of the second month after 

 conception. This state can be perceived only in the bones or 

 the parts of bones which harden somewhat late, for it is doubt- 

 ful whether those which ossify at a very early period pass 

 through the cartilaginous state, a state which appears rather 

 destined to perform the functions of bones previously than to 

 be a period of ossification. y-f.Y v ,%$$? 



The osseous state commences successively in the different 

 bones, from about a month after conception, in those which 

 ossify soonest, to about ten or twelve years after birth, in those 

 which are longest in becoming ossified. There are even cer- 

 tain accessory bony points which do not begin to form until 

 towards the fifteenth or eighteenth year. 



589. The order in which the bones begin to appear and to 

 harden, has seemed capable of being reduced to rules. 



Thus the clavicle and maxillae being very early in their de- 

 velopment, the sternum, the pelvis, and the limbs being later, 

 it has been said that the earliness is in relation to the import- 

 ance in the animal kingdom, or rather in the class of vertebrate 

 animals, where we in fact see, from the class of fishes upwards, 

 the clavicles and maxilla3 developed at a very early period, 



on the Formation of Bone, in Med. Chir. Trans, vol. vi. Loncf. 1815. A. 

 Beclard. M6m. sur fOstiose, in Nouvcau Journ. de Med. vol. iv. 1819. 

 Serres. Des Lois dc tostcogenic, Analyse des trav. de TAcad. Roy. dcs Sc. 

 1819. 



