The heart is then taken in the left hand and held by the anterior flap of the left ventricle, with the fingers inside the ventricle and the thumb on the outer surface of the anterior wall of the left ventricle, and lifted up vertically out of the pericardium. The brain-knife held perpendicularly, with cutting-edge to the right, is pushed through the right ventricular wall just to the right of the septum, carried across the cavity of the ventricle, to engage again in the ventricular wall in the line of greatest convexity, just below (anatomically) the right auriculoventricular ring, and the wall is then cut upward to the apex. The right ventricular cavity is thus opened, the fingers are introduced to explore the tricuspid ring, and the cavity and contents are inspected. The knife, held flat, is then carefully introduced through the tricuspid opening into the right auricle, the cutting edge outward, and its point thrust through the wall of the auricle midway between the superior and inferior venæ cavæ, and the auricular wall and tricuspid ring are cut upward toward the apex to meet the first incision into the right ventricle. If sufficient care is taken the incision will fall between the anterior and posterior cusps. Right auricle, tricuspid flaps and ring, and the right ventricle are thus exposed for inspection. The heart is then drawn downward and allowed to lie flat in the pericardial sac, and the pulmonary artery is then explored with the fingers of the right hand. While the anterior wall of the right ventricle is held by the thumb and index-finger of the left hand the knife is then introduced, on the flat, along the right side of the septum, into the pulmonary artery; the edge is turned upward and the point pushed through the wall of the artery, about 3 cm. beyond the ring, and a cut made toward the apex through the anterior wall of the artery, pulmonary ring and anterior wall of right ventricle, just to the right of the septum. The pulmonary artery, ring, pulmonary flaps, and right side of auricular and ventricular septum are now inspected. In cutting the pulmonary ring care should be taken to make the incision between the two anterior cusps.