eath is taken in, and contracting
each time a breath of air is expelled. It may be readily seen that if it
were not for the moistened state of the surface of the pleura the
continual dilatation and contraction and the consequent rubbing of the
parts against each other would cause serious friction.

Inflammation of this membrane is called pleurisy. Being so closely
united with the lung, it can not always escape participation in the
disease when the latter is inflamed. Pleurisy may be due to the same
predisposing and exciting causes as mentioned in the beginning of this
work as general causes for diseases of the organs of respiration, such
as exposure to sudden changes of temperature, confinement in damp
stables, etc. It may be caused also by wounds that penetrate the chest,
for it must be remembered that such wounds must necessarily pierce the
pleura. A fractured rib may involve the pleura. The inflammation
following such wounds may be circumscribed; that is, confined to a small
area surrounding the wound, or it may spread from the wound and involve
a large portion of the pleura. The pleura may be involved secondarily
when the heart or its membrane is the primary seat of the disease. It
may occur in conjunction with bronchitis, influenza, and other diseases.
Diseased growths that interfere with the pleura may induce pleurisy. The
most frequent cause of pleurisy is an extension of inflammation from
adjacent diseased lung. It is a common complication of pneumonia.
Pleurisy will be described here as an independent affection, although it
should be remembered that it is very often associated with the foregoing
diseases.

The first lesion of pleurisy is overfilling of the blood vessels that
ramify in this membrane and dryness of the surface. This is followed by
the formation of a coating of coagulated fibrin on the diseased pleura
and the transudation of serum which collects in the chest. This serum
may contain flakes of fibrin and it may be straw colored or red from an
admixture of blood. The quantity of this accumulation may amount to
several gallons.

_Symptoms._--When the disease exists as an independent affection it is
ushered in by a chill, but this is usually overlooked. About the first
thing noticed is the disinclination of the animal to move or turn
around. When made to do so he grunts or groans with pain. He stands
stiff; the ribs are fixed--that is, they move very little in the act of
breathing--but the abdomen w