38 CARTILAGE. BONE. TEETH. 



teal inflammation are explained in the same man- 

 ner. 



separation of The reparation of bones after fracture or exsec- 

 tion, or where a portion has been gouged out in an 

 operation, is accomplished by a process analogous to 

 that which the periosteum performs in ossification. 

 The gelatiniform mass which forms between the frag- 

 ments of a broken bone, in an excavation produced 

 by the gouge, or even in a medullary cavity,, contains 

 usually some fibrillae of connective tissue, together 

 with a large number of blood-globules and oval 

 nuclei (fibro-plastic), which are subsequently con- 

 verted into bone cells. It is easy to follow the suc- 

 cessive transformations of these nuclei by the micro- 

 scopic examination of a very thin lamella of bone to 

 which this gelatiniform material is still adherent. 

 These are the several steps of the process : at a little 

 distance from the bone, the oval nuclei possess a very 

 regular outline, but as we trace them nearer to its 

 surface they are observed to change their shape ; 

 their outlines wrinkle, and send out linear prolonga- 

 tions radiating in every direction; at the same time 

 earthy matter is deposited around them, by which 

 they become gradually encrusted, and thus the meta- 

 morphosis into bone is completed. (PL XXVII. 



4 1.) 



Reparation or reproduction of bone in' a medullary 

 canal, and in the cancelli of its spongy portions, is 

 not accomplished by medullary membrane, which, as 

 we have already asserted, has no existence, nor yet 

 by the aid of an imaginary cartilage, which, in any 

 case, would be but transitory. The phenomena of 



