In opening the thoracic cavity for an examination of its contents, a straight incision may be made along the central line, through the skin and superficial tissues, from the upper end of the sternum, to near the umbilicus. If it is desired to examine the abdomen at the same time, the incision may be carried on to the pubis; otherwise, ending just above the umbilicus, a transverse cut may be carried from its lower end, to the border of the chest upon either side. These incisions being carefully carried through the muscles and peritoneum, the flap thus formed may be lifted and turned up upon the chest, and the peritoneum divided along the cartilages of the ribs. The integument with the pectoral muscles may now be dissected up together, and turned back as far as the union of the cartilages with the ends of the ribs. With the heavy cartilage knife, the former may now be divided near their union with the ribs; care being observed not to permit the knife to pass into the chest, and thus injure the lungs. In aged persons, and sometimes in the middle aged, the cartilages will be found so ossified, as to require the use of the saw or chisel in the place of the knife; this being more frequently required with the first ribs, than with any other. The ligaments uniting the clavicle with the sternum, having been divided, the latter may be removed by commencing at the lower end, and separating the diaphragm from its connections to the sternum and costal cartilages. The sternum being now lifted from below, the mediastinum may be divided, this forming the only bond of union to the parts beneath, except in cases, where, from pleuritic inflammation, adhesions may exist between the lungs and costal cartilages. The sternum having thus been removed, the lungs will be found more or less collapsed from atmospheric pressure, unless adhesions be so extensive as to prevent. The attention may now be given to the pericardium and heart. By making a small opening into the cavity of the former, any dropsical fluid present may be removed and measured. This may be accomplished, by introducing the point of a syringe into the opening, and carefully drawing the fluid into the same, and then forcing it into some vessel. Or, it may be carefully absorbed by a sponge, and then squeezed out and measured.