_The common causes_ are exposure to cold, chilling winds, draughty, damp
quarters, and drinking cold water when perspiring. Injuries to the costal
pleura by fractured ribs and punctured wounds may cause it to become
inflamed.

The early symptoms of acute pleurisy are chills, rise in body temperature,
pain and abdominal breathing. The most characteristic symptom is the ridge
extending along the lower extremities of the ribs (pleuritic ridge). The
animal does not stand still as in pneumonia, but changes its position
occasionally, its movements in many cases being accompanied by a grunt.
Pressure on the wall of the chest causes the animal to flinch and show
evidence of severe pain. Large animals rarely lie down. The cough is short
and painful. On placing the ear against the wall of the chest and listening
to the respirations, we are able to hear friction sounds. After a few days
effusion occurs in the pleural cavity. Although the animal may have refused
to eat up to this time, it now appears greatly relieved and may offer to
eat its feed. This relief may be only temporary. If the fluid exudate forms
in sufficient quantity to cause pressure on the heart and lungs and
interfere with their movement, the pulse beat is weak, the respirations
quick and labored, the elbows are turned out and the feet are spread apart.
All of the respiratory muscles may be used. The expression of the face may
indicate threatened asphyxia. We may determine the extent of the pleural
exudate by auscultation. There is no evidence of respiratory sounds in that
portion of the chest below the surface of the fluid. Dropsical swellings
may occur on the under surface of the breast and abdomen.

_In subacute cases_ evidence of recovery is noted in from four to ten days.
_Acute pleurisy_ very often terminates fatally. Under the most favorable
conditions, recovery takes place very slowly, sometimes extending over a
period of several months. It is not uncommon for the horse to continue