476 STERNAL SINUS. 



of the rib. General disturbance is commonly wanting ; symptoms 

 of pleurisy only occasionally occur, but when they do, almost in- 

 variably result in death. 



Prognosis. The sequestrum prevents healing ; whether it can 

 be removed depends on its size and position, and to ascertain this, 

 operative interference is usually necessary. Prognosis is more 

 favourable where the process is confined to the external surface of 

 t he lib ; but where it extends to the inner surface the condition becomes 

 chronic, and pleurisy may supervene. The latter condition is 

 indicated by the difficulty in breathing and the relatively copious 

 discharge. But even with chronic necrosis of the outer surface, 

 animals may remain useful for a long time. 



Treatment. The direction and extent of the sinus has first to 

 be discovered, bearing in mind that the middle of the swelling is 

 the point beneath which the chief alterations exist. The sinus 

 should be laid open freely, especially if it trends downwards, care 

 being taken not to wound the external thoracic vessels. The exposed 

 rib is scraped with a curette, the necrotic bone removed, and healing 

 encouraged. Sinuses which cannot be laid open may be treated 

 with antiseptics and astringents, such as liquor Villati, carbolic, 

 or sublimate solution. When the sinus extends to the inner surface 

 of the rib, non-irritant substances are selected. After removal of 

 large pieces of bone, deep scars often remain in the chest wall. The 

 resection of a piece of rib, although not easy, and involving danger 

 of perforating the pleura, was effected in the horse by Ferguson 

 sixty years ago, and may occasionally be necessary. In such case 

 the necrotic portion is exposed by a long incision through the skin 

 and subcutaneous tissues and periosteum. The periosteum is 

 separated from the deep face of the rib, great care being taken not 

 to perforate the pleura nor to injure the intercostal artery, which 

 passes down the posterior face of the bone. The necrotic part is 

 then removed by strong bone forceps. A drain is inserted in the 

 lower part of the wound, which is sutured and covered with a 

 dressing. 



III.— STERNAL SINUS AND FRACTURE OF THE STERNUM. 



Sternal sinus is a condition almost entirely confined to the horse, 

 in which, however, it is not uncommon, and is due to suppuration 

 dependent on local necrosis of the sternum. 



The sternum consists of a mass of spongy bone, and in horses 

 is especially liable to be injured by falling or lying on uneven ground, 



