164 PRINCIPLES OF YETERINAEY 8UKGEET 



What is the difference between the provisional and permanent 

 callus ? 

 Both, are the same product of a process of regeneration, 

 only in different stages of development. 



What are osteoclasts ? 



These are mnltinuclear giant cells supposed to have the 

 power to form free carbon dioxide and thus dissolve the 

 lime salts of the hones and absorb bony substance. 



What is a synosteosis ? 



The permanent union of two single parallel bones by a 

 callus ; for instance, in fracture of two adjoining ribs. 



What is an anchylosis ? 



A stiff joint. Here the articulating extremities of two 

 Ijones are rendered immovable by a callus. 



What is a fibrous callus ? 



One which, instead of being composed of bone, is made 

 Tip of fibrous tissue. In other words, the callus never reached 

 & bigher development than the fibrous stage. Seen in frac- 

 tures of bones witb limited blood supply, insufficient immo- 

 bilization of the fragments and in those where the fragments 

 were drawn apart to considerable extent : false ribs, patella, 

 pisiform bone, olecranon, etc. 



What two processes is the ossification of the callus the result 

 of? 

 It is the result of an ossifying periostitis and osteomye- 

 litis. 



What is a pseudoarthrosis f 



It represents an ununited fracture ; tbat is, the broken 

 ends show mobility, being held together by fibrous union ; 



