256 DISEASES OF THE HORSE. 
responding to the frequency of the heartbeat. This is known as a 
friction sound. Between the second and fourth days this sound may 
disappear, due to a distension of the pericardium by an exudate or 
serous effusion. As soon as this effusion partly fills the pericardium, 
percussion will reveal an abnormally increased area of dullness over 
the region of the heart, the heartbeats become less perceptible than 
in health, and in some cases a splashing or flapping sound may be- 
come audible. : 
If the effusion becomes absorbed, the friction sound usually recurs 
for a short time; this friction may often be felt by applying the 
hand to the side of the chest. In a few cases clonic spasms of the 
muscles of the neck may be present. In acute pericarditis, when the 
effusion is rapid and excessive, the animal may die in a few days or 
recovery may begin equally as early. In subacute or in chronic cases 
the effusion may slowly become augmented until the pressure upon. 
the lungs and interference with the circulation become so great that 
death will result. Whether the attack is acute, subacute, or chronic, 
the characteristic symptoms which will guide us to a correct diagnosis 
are the friction sound, which is always synchronous with the heart’s 
action, the high temperature with hard, irritable pulse, and, in cases 
of pericardial effusion, the increased area of dullness over the car- 
diac region. When the disease is associated with influenza or rheu- 
matism, some of the symptoms may be obscure, but a careful exami- 
nation will reveal sufficient evidence upon which to base a diagnosis. 
When pericarditis develops as a result of or in connection with pleu- 
ritis, the distinction may not be very clearly definable, neither will 
many recover. When it results from a wound or broken rib, it 
almost invariably proves fatal. 
Pathology—Pericarditis may at all times be regarded as a very 
serious affection. At first we will find an intense injection or accu- 
mulation of blood in the vessels of the pericardium, giving it a red 
and swollen appearance, during which we have the friction sound. 
In 24 to 48 hours this engorgement is followed by an exudation of 
sero-fibrinous fluid, the fibrinous portion of which may soon form a 
coating over the internal surface of the pericardial sac, and may 
ultimately form a union of the opposing surfaces. Generally this 
adhesion will only be found to occupy a portion of the surfaces. As 
the serous or watery portion of this effusion is absorbed, the dis- 
tinctness of the friction sound recurs, and may remain perceptible in 
a varied degree for a long time. When the serous effusion is very 
great, the pressure exerted upon the heart weakens its action, and 
may produce death soon; when it is not so great, it may cause dropsies 
of other portions of the body. When the adhesions of the peri- 
cardial sac to the body of the heart.are extensive, they generally lead 
to increased growth, or hypertrophy, of the heart, with or without 
