MODES OF UNION. 83 



either fibrous or cartilaginous, or may assume a structure inter- 

 mediate between these, and in any of these cases ossification may 

 ensue. In different specimens, or sometimes in different parts 

 of the same, the reparative material has in one displayed fibrous 

 tissue with a few imbedded corpuscles, like the large, nearly 

 round, nuclei of cartilage cells ; in another, a less appearance of 

 fibrous structure, with more abundant nucleated cells, havimr 

 all the characters of true cartilage cells ; and in another, a yet 

 more nearly perfect cartilage. Through any of these structures 

 the reparative new bone may be formed. It may be formed, 

 first, where the reparative material is in contact with the old 

 bone, and thence extending, it may seem as if it grew from the 

 old bone ; it may be also formed in the new material in detached 

 centres of ossification, from which it may extend through the 

 intervening tissues, and connect itself with the old bone. 



The new bone, by whatever mode it is formed, appears to 

 acquire its proper microscopic characters. Its corpuscles, or 

 lacunae, at first simple, round, or oval shaped, become jagged 

 at their edges, and subsequently acquire their canals, which 

 appear to be hollowed out in the pre-formed bone as minute 

 channels communicating with one or more of the lacunae. The 

 laminated canals for blood-vessels are later formed. At first, all 

 the new bone forms a minutely cancellous structure, which is 

 light, spongy, soft, and succulent, with a reddish juice, rather 

 than marrow ; and is altogether like the bones of the foetus at 

 their first construction. But it gradually assimilates itself 

 to the structure of the bones that it repairs, its outer portions 

 assuming a compact laminated structure, and its inner acquiring 

 wdder cancellous spaces and a more perfect medulla. It acquires 

 a definite periosteum, which is at first thin and lamellar, but 

 gradually assumes toughness and compactness. 



Eepair of fracture by formation of a false joint is an arrest- 

 ment of the process before ossification has commenced. 



TREATMENT OF FRACTURES. 



In the treatment of a fracture, it is of great consequence to 

 perform reduction as soon as possible after the injury is sus- 

 tained, in order to prevent the bad effects of continued irrita- 

 tion, and before the occurrence of sw^elling and thickening of tlie 



