bones: diseases axd accidexts. 273 



have extended to some of the adjarent tissues, and even though the 

 fracture mnj be of the simplest type there is almost sure to be con- 

 siderable hemorrhage around the ends of the broken bone. This, 

 howe^'er, is unimportant if the skin remains intact, unless a very 

 large vessel should be injured, or the fracture should open some of 

 the important cavities of the body, in vrhich case a fatal hemorrhage 

 may result. If, on the other hand, the fracture is compound the 

 external opening furnishes a fertile field for the lodgment of disease- 

 producing germs. 



Unless great care is taken in such cases, a suppurative process is 

 liable 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 

 if 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 liable to be imprisoned, and, burrowing 

 downward, saturate the whole striicture, 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 fii-mer till it forms a 

 callus, known as the external or ensheathing callus, in the shape of 

 a ring or ferrule surrounding the detached portions of the bone. It 

 occasionally happens that this callus forms only 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 de- 

 tached 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 eifused lymph, which is ultimately to constitute the tem- 

 porary cartilage, takes it 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 fibrocar- 

 tilaginous structure undergoes a change and is gradually converted 

 into bone, forming a ferrule on the outside and a plug on the inside, 

 33071°— 16 18 



