170 VETERINARY SURGICAL THERAPEUTICS. 
the tissues, of irritant infectious liquids, scarifications and antiseptic 
injections must be made. Emphysema of sheep can be avoided by 
smoothing the canine teeth of dogs which watch the flock. When a 
bite is already accompanied with emphysema, a free cutting away of 
the skin, at the wound, will prevent its spreading. 
The benignity of essential emphysema is like that of localized em- 
physema. It ordinarily disappears in a few days, sometimes even in 
afew hours. Massage is-useful. Scarifications, recommended by 
Lafosse, are superfluous. 
IV. 
THROMBOSIS AND TRAUMATIC VENOUS EMBOLISM. 
Any vein enclosed in a traumatic center is: exposed to thrombosis ; 
inflammation may affect its walls, alter its endothelial layer, and thus 
produce coagulation of the blood in the blood-vessel; if the walls 
have been injured, thrombosis almost always starts immediately. Some- 
times the clot increases gradually, obliterates the vessel, and extends 
forward even to the first collateral (obiiterating thrombosis); at other 
times the coagulation remains still and the canal is yet permeable (fa- 
rietal thrombosis). When the diseased vein is enclosed in a non-infected 
traumatic center, the intravascular clot is also aseptic. It is habitu- 
ally infected in venous thrombosis which occurs in suppurating wounds. 
In general, aseptic clots quickly adhere somewhat intimately to the 
walls of the blood-vessel; they are soon infiltrated with embryonic 
elements, and become the seat of an organization which ends with the 
obliteration of the vein by a fibrous tissue continuous with the vascular 
walls. Sometimes it happens that they disintegrate; portions may get 
loose from their central extremity, continuously struck by the blood at 
the very point where the circulation is still going on. 
It is thus that, emboli or erratic clots are produced, which, carried by 
the blood, go to produce infarction in the lungs, by obliterating the 
small divisions of the pulmonary artery. Unless voluminous, aseptic 
emboli give rise to troubles, not serious, beginning in hyperemia and 
ending in sclerosis of the thrombotic pulmonary territory. What 
makes the gravity of traumatic thrombi, or of the emboli that get loose 
from them or of the infarctions which produce them, is zwfection. Septic 
or malignaut emboli carry into the lungs infectious agents with various 
virulency which give rise to metastatic abscesses or to centers for gan- 
grene. 
Voluminous emboli sometimes close a principal branch of the pulmo- 
nary artery; at others, they are arrested by the valvular cords of the 
right ventricle. Whether aseptic or infected, they suddenly provoke 
serious troubles, sometimes death in a few moments. 
