Emphysema, a term applied to an unnatural accumulation of air in some tissue of the body. In wounds of the chest wall, where the lung is injured and air escapes into the textures surrounding the damaged parts, a condition which is spoken of as surgical emphysema is produced. Emphysema proper is a peculiar affection of the lungs in which the air cells become dilated. On examination of an emphysematous lung a number of blebs are seen to project from its surface, and on throwing the diseased organ into water it is found to possess an unnatural buoyancy due to the distension of its vesicles with air. Emphysema is very apt to occur in association with repeated attacks of bronchitis; indeed, in this connection, it is one of the commonest diseases met with in persons beyond middle age. The symptoms produced by the condition are shortness of breath, duskiness of the skin due to deficient aeration of the blood, and often some degree of emaciation. Long-standing emphysema usually affects the heart by interfering with the circulation of blood through the lungs. The treatment of emphysema mainly resolves itself into dealing with the associated bronchitis; taking every precaution against cold, careful dieting, and in some cases removing the patient to favourable atmospheric surroundings.