III. DISEASES OF THE THOEAX. 
I.—FRACTURES OF THE RIBS—FRACTURE COSTARUM. 
Fractures of the ribs are usually produced in the larger domesticated 
animals by external violence, by thrusts from carriage-poles, kicks, falling 
on uneven hard ground, unskilful casting, and in the case of runaways 
by collisions with obstructing objects ; in ruminants, from blows with the 
horns ; and in smaller animals from treads with the foot, 01 falling fiom 
considerable heights. Contused fractures are most common. Breakage 
seldom results from excessive muscular action, though Stockfleth has 
seen fracture of the first ribs produced in horses drawing heavy loads. 
Fractures of the ribs seem most frequent in swine, but are usually 
discovered only after death. Charpentier and Lafourcade, from obser¬ 
vations in the slaughter-houses, found that 15 per cent, of swine had 
suffered fractures of the ribs, many of which had completely united. 
Simple transverse fractures are most common ; but sometimes the fracture 
is incomplete, the concave surface bending inwards, and the periosteum 
occasionally remaining uninjured (subperiosteal fracture). Less fiequent 
are compound fractures, involving injury to the skin. In such fractures 
the pleura and lungs, or the peritoneum and abdominal walls, are some¬ 
times injured. In a case of Grosswend’s, a horse’s last rib having been 
fractured, the fragments perforated the omentum and stomach. 
The course taken is determined by the form and variety of the injury. 
Partial and simple subcutaneous fractures of the anterior ribs usually 
unite completely without marked symptoms. The great mobility of the 
posterior ribs interferes, however, with their union ; a callus fibrosus, or 
pseudoarthrosis forms, but does not impair health, and, indeed, is often 
only discovered after death. 
Compound fractures, involving perforation of the skin, may lead to 
pus formation and necrosis of bone ; but healing, even though long 
delayed, occurs. Should the sequestrum not be removed, a costal sinus 
may, however, develop (see page 219). 
When the pleura, lung, or peritoneal cavity is involved, the consequences 
are much graver. In penetrating injuries of the thorax, air fiom the lungs 
frequently enters the pleural sac, but is commonly absorbed as quickly as 
the emphysema ; for it has been found that air does not contain infectious 
materials in as large amount as was formerly believed, and poitions of 
