206 PRINCIPLES OF VETEEINABT SUKQEEY 



changes in the parts involved. Therefore, in the former tha 

 displaced bone is not yet fastened by tissue changes in tha 

 place into -which it was forced, while in an old dislocation the 

 displaced bone is held firmly in its new location by tissua 

 changes. 



What is relapsing or habitual luxation ? 



It is a dislocation recurring frequently and from slight 

 cause. 



Depending on the cause, what forms of dislocations a/re recog~ 

 nized ? 



1. Traumatic dislocations : Due to sudden force. 



2. Pathological or spontaneous luxations : Due to inflam- 

 matory and other pathological processes. 



3. Congenital dislocations : Due to a congenital malfor- 

 mation of the joint. 



Sow does sudden force produce traumatic luxations ? 



The joint is either dislocated directly by a blow of some 

 sort, the latter driving the articular ends apart, or external 

 violence may act indirectly in this way : A bone struck at a 

 distant part transmits the force of this blow to its end, which 

 drives it (the bone) out of the joint. Finally, sudden and 

 severe muscular contraction may be an active cause of luxa- 

 tion by pushing the head of the bone powerfully against the 

 weakest part of the ligaments retaining the articular ends. 



Give some examples of traumatic dislocations. 



In the horse, the more common ones, although not as 

 frequent as fractures, are upward dislocation of the patella 

 by sudden powerful contraction of the triceps f emoris, as seen, 

 in kickers ; luxation of the cervical vertebrae (not a rare sight 

 when a lot of bronchos undergo training) ; dislocation of the 



