Pleurisy is an inflammation of the pleura, a serous membrane which envelopes the lungs and also lines the inside of the chest. It may be acute or chronic, and mild or severe, the disease may be limited to one side of the chest or it may include both sides.

This disease can attack people of all ages, from children right through to the very elderly. Like any other viral infection, pleurisy can occur in small epidemics.

The membranes that cover the lung are called pleura. The outer membrane, known as partial pleura, is applied to the inner wall of the thorax, and the inner membrane, known as the viscerall pleura, covers the substance of the lungs. 

There is a capillary space between the two membranes which is filled with fluid. This fluid enables the lungs to move freely in the chest.

The parietall membrane is reflected from the chest wall to cover the upper surface of the diaphragm, and in the midline, it covers the mediastinum, the partition which separates the two sides of the chest and contains the heart, great vessels and other structures which run through the thorax.

The onset of pleurisy is generally marked by a sharp and stabbing pain, which may be felt in any part of the chest wall or over the diaphragm. Deep breathing or coughing increases the pain. In many cases, the disease begins with a chill, followed by congestion of the pleura and later by fever. The degree of the fever determines the severity of the disease. The inflammation destroys the tissues and chokes the circulation within the tissues. Breathing becomes difficult due to the clogging of the circulation, and by pain and swelling within the chest. Later a liquid effusion escapes from the pleura, filling the open spaces in the chest cavity until the effect of the distension becomes oppressive. After absorption takes place or after the drainage of the effusion, the pressure is lowered, the pain is reduced and the patient feels relieved. It is sometimes dry pleurisy, a form where there is little or no effusion or the effusion may be circumscribed. The effusion may become gangrenous, or become mixed with blood, or be of a dirty brown color with an offensive odor, leading to great suffering.

Catching a cold followed by congestion and swelling of the pleurall membrane. It is a disease that is not caused by germs. There will be germs of putrefaction later in the ooze of serum from the tissue the disease may be a complication of pneumonia, or pneumonia may be a complication of pleurisy. In a few cases, the diseases may also occur in rheumatic fever, uraemia and other conditions.