OP THE BONES. 373 



towards the middle of the fourth month, in the ossicula tym- 

 pani; at mid term, in the pubis, the calcaneum, the second 

 phalanges of the toes, the lateral masses of the ethmoid bone 

 and the turbinated bones of the nose; a little later in the first 

 pieces of the sternum; towards the sixth month, in the body 

 and odontoid process of the second vertebra, and in the lateral 

 and anterior masses of the first pelvic or sacral vertebra; a 

 little later still, in the astragalus; towards the seventh month, 

 in the sphenoidal turbinated bone; at a later period, in the 

 median ridge of the ethmoid bone; towards the period of birth, 

 in the os cuboides, the first vertebra of the coccyx and the 

 anterior arch of the atlas; a year after, in the coracoid bone, 

 the os magnum and os unciforme of the carpus, and in the 

 first cuneiform bone; about the third year, in the patella and 

 pyramidal bone; about the fourth year, in the third and second 

 cuneiform bones; about the fifth year, in the os scaphoides of 

 the tarsus, the trapezium and os lunare; towards the eighth 

 year, in the scaphoid bone of the carpus; a year after, in the 

 os trapezoides, and lastly, about the twelfth year, in the os 

 pisiforme. 



591. Ossification does not everywhere result from the 

 transformation of cartilage into bone. The diaphysis of the 

 long bones and the centre of the broad bones, which are deve- 

 loped at a very early period, pass immediately from the .mu- 

 cous to the osseous state. The other parts of the system are 

 at first cartilaginous, and it is in them that the successive phe- 

 nomena of ossification may be best observed. 



The cartilage, which for a longer or shorter period takes 

 the place, and performs the functions of the bone of which it 

 has the form and of which it gradually acquires the volume, 

 is at first hollowed with irregular cavities, then with canals 

 lined by vascular membranes filled with a mucilaginous or 

 viscous fluid; it becomes opaque, its canals become red, and 

 ossification commences towards its centre. 



The first point of ossification, punctum ossificationis, al- 

 ways appears in the substance of the cartilage, and never at its 

 surface. It is surrounded by red cartilage at the place which 

 is in contact with it, opaque and full of canals at a little dis- 



