This most painful disease, like those of the lungs generally, visits valuable horses during the years when they are most esteemed. The unbroken colt is seldom attacked, and the aged animal is, to an almost equal degree, exempt. The young steed, newly stabled, is liable; and that liability remains up to the sixth year, when it gradually subsides. It is a terrible affliction. Its anguish is localized and concentrated. It is inflammation of the fine, glistening membrane covering the lungs and lining the inside of the chest. At every inspiration and at every expiration the inflamed surfaces must move upon each other. To breathe is the primary necessity of the creature's life. It cannot exist and refuse to inflate the lungs; yet is existence purchased at a price worth many years of happiness. The inflamed surfaces cannot remain quiet; yet, to render the condition of motion the more acute, inflammation stops the secretion, which, during health, smoothed and lubricated the passage of the membranes. During disease, the pleura is swollen, rough, and dry; it grates or scratches as one surface is, by the necessity to breathe, dragged over the other. Membranes are sensitive in disease in proportion to the fineness of their structure, and to their insensibility during health. The pleura belongs to what are termed serous membranes. These line closed cavities; as the chest, the abdomen, and the joints. Of the existence of none of these are we conscious while they are free from disease; but, let the inflammation set in, and it would be difficult to decide which of them is the most painful. Fortunately, however, =pleurisy=, when concentrated or singly present, terminates generally by the second day.