88 FRACTUKES AND DISEASES OF BONES. 



to suffer separation from them by such accidents or violence as 

 would — later in the animal's life, and when the process of ossifi- 

 cation had become complete — occasion fracture. The symp- 

 toms and treatment are the same as those of fracture. 



FALSE JOINTS AND NON-UNION. 



Fractured bones sometimes do not unite firmly together, their 

 extremities remain quite detached, or are merely connected by a 

 fibro-cartilagjinous structure. 



The constitutional causes so common in man do not, as a 

 rule, aj^ply to the lower animals, but occasionally it is found 

 that a condition of the osseus system, termed mollities ossium, 

 and another partaking of the nature of necrosis, exist, and effec- 

 tually prevent reunion of the bones. The most common cause 

 of false joint is the want of, or the impossibility of securing, 

 proper apposition of the fractured ends ; and its most frequent 

 situation, the anterior spinous process of the ileum. Indeed, 

 it can be safely said that this fracture always ends in a false 

 joint. When broken, the legs of dogs are sometimes united 

 in this way, even after every precaution has been taken to 

 secure all the essentials of recovery. This termination of the 

 healing process may be looked upon as an example of arrested 

 development of the reparative material ; every part of the pro- 

 cess of repair being complete except that of ossification; the 

 fragments being held together by a yielding and pliant band. 



In order to secure perfect reunion of the fractured ends of 

 bones, it is necessary — (1st.) That little or no motion should exist 

 between them : (2d.) That there be no excess of inflammatory 

 action : (3d.) That there be no interposition of pieces of muscle, 

 tendon, or necrosed bone between the fragments; and (4:th.) 

 That there be a proper supply of blood to the part. Curling, 

 Guerton, and others have paid attention to this subject, and 

 have shown that non-union, as well as atrophy of bone, may be 

 due to defective supply of blood, caused by rupture of the 

 nutrient artery of the broken bone. 



It is found that if the supply of blood be cut off by injury 

 to the nutrient artery, so tliat the periosteum has exclusively 

 to supply the blood, either one or both of the fractured 

 pieces become atrophied, and their cancellated structure and 

 walls thinned. While writing this paper, I had an oppor- 



