Those who recollect the remarkable results which Abernethy sometimes obtained in regard to this intractable and often formidable class of diseases, will, I think, be disposed to agree in thinking that few maladies are more open to improved investigation, or promise a more encouraging prospect of enlarging the boundaries of philosophical medicine. SECTION. HIS PAPER ON A CURIOUS CIRCUMSTANCE SOMETIMES FOLLOWING INJURY TO THE LUNGS. Fractured ribs are common accidents, and illustrate very beautifully those conservative principles in animal bodies which give such interest to the study of their economy. When first we consider that the ribs form the greater part of that box in which the lungs and heart are enclosed, and by which they are protected, we are disposed to regard a fracture of one or more ribs as a very serious affair. Nevertheless, these accidents generally do extremely well. In the first place, the gristles, or cartilages as they are called, by which the ribs are attached to the sternum in front, give, in conjunction with the spine behind, considerable elasticity to the whole structure of the chest. Most injuries have therefore to overcome this elasticity, before anything gives way; and when the rib has done so, and is fractured, the resiliency of the cartilage or gristle to which it is attached _tends_ to restore it to its place, or to set it, as we phrase it. Another very curious thing in accidents is the instantaneity with which muscles which are _ordinarily_ under the dominion of the will, become reluctant to obey it, or altogether repudiate its authority. In all fractures, of course, the most material thing is absolute repose; and there is very little chance of a man moving his rib when it is broken. He instinctively begins to expand his chest, for the admission of the necessary air, by other muscles, usually to the exclusion of those which are attached to the broken bone. The Lung, which may be considered as a series of tubes, some conveying blood, and others air, is often wounded; but the blood immediately stops the leak, from its tendency to coagulate when out of the vessels; and no harm ensues. Occasionally, however, a circumstance occurs, which, until it is understood, appears curious and alarming. Either from the extent, the scratching of the surface, or some other peculiarity in the wound of the lung, the air escapes from it, and the patient is as it were blown up, as to the chest, neck, and face, by the air impelled from the lung beneath the skin into the connecting tissue, exactly in the same manner as the butcher does when he is preparing veal. This blowing-up is called, from the Greek word for it, _Emphysema_; and it was on this feature in these accidents that Mr. Abernethy wrote a short paper.