bones: diseases and accidents. 281 



Unless great care is exercised in such cases a suppurative process 

 is likely to be established which will seriously interfere with, if not 

 entirely arrest, the process of union between the bones; or it may 

 become so serious as to endanger the general health of the animal 

 and even be attended with fatal results. This last danger is greater 

 where the injury has occurred to the bones of the arm or thigh. In 

 such cases, owing to the dense covering of fascia which ensheathes 

 the muscular covering, pus is likely to be imprisoned, and. burrowing 

 downward, saturate the whole structure, not only endangering the 

 limb, but, by absorption, may set up blood poisoning and seriously 

 interfere with the general health of the patient, even to causing 

 death. In order so far as possible to prevent such an unfortunate 

 complication, the wound should be carefully cleansed with a mild 

 solution of carbolic acid, then dusted over with iodoform before the 

 bandages are applied, and cleansed and dressed daily in the same 

 way. After dressing always cover with absorbent cotton. In the 

 early process of union an exudation of lymph takes place, which is at 

 first fluid, gradually becoming thicker and firmer till it forms a callus 

 in the shape of a ring or ferrule surrounding the detached portions 

 of the bone. knoAvn as the external or ensheathing callus. It occa- 

 sionally happens that this callus only forms at the ends of the bones, 

 filling the spaces that exist between them, when it is known as the 

 intermediate callus. The process of union may be divided into five 

 stages. In the first stage, including the first eight days, the detached 

 portions of the bone and the sharp projections that are not sufficiently 

 nourished are absorbed ; the blood which escaped into the surrounding 

 tissues, the result of the injury, is gradually absorbed, and the effused 

 lymph, which is ultimately to constitute the temporary cartilage, 

 takes its place. In the second stage, from the tenth to the twentieth 

 day, the tumor or callus is formed and fibrocartilage is developed 

 inside and around the exposed end of the bone. In the third stage, 

 extending from the twentieth to the fortieth or fiftieth day. according 

 to the age and strength of the animal, the fibrocartilaginous structure 

 undergoes a change and is gradually converted into bone, forming 

 a ferrule on the outside and a plug on the inside, which serve to hold 

 the part in position. In the fourth stage, extending to about the 

 sixth month, the whole of the new structure is converted into bone. 

 In the fifth stage, extending up to the end of the first year, the callus 

 is absorbed, being no longer necessary, and the connection between 

 the cavities of the two bones is again established. 



Comtnon complications. — The process of union just described is 

 healthy and normal. Diseased conditions may at any time supervene 

 during the treatment and render the operation unsuccessful. In the 

 case of compound fracture, the open wound communicating with the 



