DEVELOPMENT OF BONE. 



neous fluid mass, not having any characters hy which the 

 one can he distinguished from the other. 



Ahout the expiration, however, of the first month after 

 conception the mucous stage "becomes converted into the 

 cartilaginous, which greatly increases the consistence of 

 hone, and is the commencement of form in the foetus. 

 Agreahly to the observations of Bichat and Scarpa, the 

 cartilaginous condition presents two peculiarities. The 

 first is_, that during the formation of cartilage we do not 

 see the longitudinal strige of the long hones, the radiated of 

 the flat, nor the mixed of the thick, which distinguish the 

 osseous or third stage. The second peculiarity is, that all 

 those hones which are to he united hy cartilage in the adult 

 skeleton, are in one piece, as those of the vertebrae and pel- 

 vis, while those which are to he united hy ligament, and, 

 consequently movahle, are isolated, as the femur, tibia, &e. 



The cartilaginous condition is complete at the end of the 

 first or beginning of the second month, when the third or 

 osseous stage commences. This event is announced by the 

 arrival of red blood, which first shows itself in the centre 

 of the cartilage, and the spot receives the name of the 

 "punctum ossificationis" or point where ossification first 

 commences. It appears that until this period it is not in 

 direct relation with the blood, but, according to Carpenter, 

 is surrounded by blood vessels which have "large ampullae 

 or varicose dilatations," from whence, and by imbibition, it 

 is nourished. 



The manner of ossification is somewhat modified in the 

 three classes of bones. In the long bones there is first seen 

 a central ring, whose cavity is the commencement of the 

 medullary canal. This ring, forming the bony nucleus, 

 gradually grows in length and thickness till the period of 

 birth arrives, when we have the body or diaphysis gene- 

 rally finished. The epiphysis, or extremities of the long 

 bones, do not commence ossifying till after birth, when we 

 observe the point of ossification, as in the body, occupying 

 the centre and extending towards the shaft. This process 

 is not entirely complete, so that the different parts become 



