126 
DEPARTMENT OF SURGERY. 
always a secondary condition, but it does not always result from 
the effect of inflammation. It may be accompanied by anasarca 
and ascites, or may exist alone, but never exists as the only 
malady. We may mention in a general way that it is liable to 
arise under the following circumstances: 
1. As a sequel of acute pleurisy. 
2. From “ quiet ” pleurisy. 
3. When the whole circulation is impeded, and the venous 
pressure is increased, e . g. : 
( a ) Mitral or tricuspid insufficiency. 
(£) Diseases of the orifice of mitral or tricuspid valve. 
4. When venous stasis is due to local causes, viz. : 
(a) Focalized swellings or tumors over veins. 
( b ) Thrombosis. 
5. When renal diseases lessen the elimination of the watery 
portion of the blood. 
6. When the parietal and visceral lymphatic glands are en¬ 
larged and indurated ; and when the functional activity of the 
stomata of the pleura is impaired by inflammation or other¬ 
wise. 
7. When the quality of the blood is changed by disease ; or 
the circulation impeded by cold or other general influences which 
favor exudation of serum from the blood vessels. 
V 
Diagnosis. —In the horse hydrothorax is always bilateral, 
while in other animals it may be unilateral. The diagnosis is 
generally easy unless the fluid is confined to a portion of the 
thorax by pleuritic adhesions. Dyspnoea is the most important 
symptom. By auscultation a dull section is found extending 
along the lower portion of the thorax {longitudinally) and ter¬ 
minating abruptly above; the line of demarcation between the 
portion filled with fluid and the empty part superiorly will vary 
as the position of the patient. Sometimes the recognition of 
other dropsical conditions is very suggestive. When the symp¬ 
toms point to hydrothorax the trocar should be used to verify 
the diagnosis. The fluid, if entirely non-inflammatory, appears 
as a greenish or reddish transparent fluid ; it does not contain 
clots, nor coagulate in the vessel. It contains a little albumen, 
and its specific gravity varies from 1005 to 1010. 
The presence of corpuscular precipitates ; a tendency to 
coagulate ; or any turpidity of the effusion, is suggestive of 
inflammation. When it is streaked with blood, the condition 
is an indication of venous stasis or arterial degeneration. The 
cavity may contain pus, cretified pus, with or without secondary 
