404 DISEASES OF THE AIR-PASSAGES OF HORSES. 
and associate of broken-wind, its principal phenomena are, an ha¬ 
bitual cough, a slight expectoration of a bluish mucosity, which 
in some cases is so trifling as to escape observation unless the 
water-pail is examined, an increased desire for food and water, 
and an absence of the appreciable symptoms of fever. 
This inflammatory action continues in its low grade of proces¬ 
sion, advancing through the subdivisions of the bronchi. The 
mucous membrane becomes thickened, together with the submucous 
tissue. The secretion is changing in quality to a more adhesive 
and viscid consistence. The muscular function of the bronchial 
tubes is impeded, together with the vital expansive power of the 
lungs themselves. The ingress and egress of air to and from the 
air-cells is gradually growing more difficult, and the changes in 
the blood proportionately lessened. The delicate tissue of the ex¬ 
treme subdivisions of the air-tubes and of the cells is endangered 
with laceration in ordinary respiration, and exertion of the animal, 
by coughing or otherwise excites the whole mechanism of respi¬ 
ration to increased action. Thence ensues the rupture of some 
part of the above structures, and emphysema of the lung takes 
place; a condition or anatomical character pathological of broken- 
wind. 
In the secondary or consecutive form of chronic bronchitis, either 
of the sthenic or asthenic forms of the disease, when productive of 
permanent impaired respiration, the changes on the mucous and 
sub-mucous tissues are more frequently that of softening existing 
with thickening; and, this state of the structure extending to the 
cells, gives rise to dyspncea, proportionate in severity with the ex¬ 
tent of alteration in the above tissues. 
This condition of the structures of the bronchi and air-cells is a 
great impediment to the vital changes upon the blood; a conse¬ 
quent deterioration of that fluid produces a comparative excite¬ 
ment in the organic vascular system of respiration, and much assists 
the causes of structural alteration, in the establishing of incurable 
dyspnoea. 
In closing this essay, I would recommend the profession—and 
I do so with due consideration—to consider broken-wind as emphy¬ 
sema of the lungs in complication with chronic bronchitis. This 
is the pathological condition and true form of the disease. 
Dyspnoea and orthopnoea may occur from other lesions besides 
those I have enumerated; as accidents to the diaphragm, dilata¬ 
tion of the bronchi, &c.; but these are anatomical characters ab¬ 
sent in fort 3 '--nine horses out of fifty said to be broken-winded 
during life. 
The phenomena furnished by auscultation are conclusive, and 
enable us to point out the disease blindfolded. The icheeze, 
