Practical pathology

by Aldred Scott Warthin

2. Thymus. The thymus is then examined by means of transverse cuts; or, when large, is dissected from below upward, turned up onto the neck, and removed later in connection with the neck organs. When no traces of thymic tissue are visible to the naked eye the thymic fat should always be cut transversely and examined for the presence of small lymphoid nodules. In the case of hypertrophic thymus the question of pressure upon the trachea becomes of very great importance, and, to settle this, the trachea should be opened above the sternum before the thymus is removed; or the thymus may be taken out in connection with the trachea and both sectioned horizontally at the same time. In cases of sudden death, in which the thymus may be an etiologic factor, it is safest to examine the trachea from above the sternum before the thorax is opened, or to fix the whole body (infant’s or child’s) in formalin and then to remove thymus with trachea, and examine by means of transverse sections.

The heart is examined before the lungs chiefly for two reasons: Its blood-content can be more accurately determined, and the blood caught in the pericardial sac, so that when the pulmonary vessels are cut in the removal of the lungs there is no gush of blood into the pleural cavity.

3. Pericardial Sac. This is next examined with respect to the degree of intrapericardial tension. Its anterior wall is then picked up at about its middle by the thumb and index finger of left hand, and the point of the long section-knife, with cutting edge outward, is pushed through the pericardium and a small slit made into the sac. The escape of gas or air should be noted at this time. A sterile pipette may now be introduced and the fluid contents of the sac secured for bacteriologic examination; or before the pericardial sac is opened the pericardium may be seared with a hot iron and a sterile pipette pushed through it into the cavity. The longitudinal incision through the pericardium is now extended upward to its attachment to the great vessels, and through the opening thus made the character and amount of the pericardial fluid are determined. The incision is then extended to the left at its lower end by cutting the sac-wall toward the apex of the heart. Through the three-cornered incision thus made the heart is lifted out of the sac and the surfaces of the parietal and visceral layers of the pericardium examined. Localized adhesions of the pericardium may be cut or torn, extensive or complete adhesions may be separated when this is possible; if this cannot be done, the pericardial layers are cut with the heart wall.

4. Section of the Heart. The heart may be examined either in the body or outside. The choice of several methods may be taken, and the one most convenient and easy of performance is advised, rather than a method based upon such considerations as the direction of the blood-current in the normal body. The chief essential is to expose completely the interior of the heart with the least possible disturbance of anatomic relationships, and to accomplish this in the simplest and easiest way. Such a method must leave the heart in such shape that it can be reconstructed for histologic study or utilized as a museum specimen. This can be accomplished by a modified Rokitansky method, as follows:

The heart is first carefully inspected as it lies in the pericardial sac. The apex is then lifted in the left hand and the posterior wall inspected. The heart is then drawn up over the right edge of the ribs, so that the left border of the heart presents uppermost as the line of greatest convexity. The point of the narrow brain-knife (amputation-knife), with cutting edge upward, is then inserted through the wall of the left ventricle at the apex, just to the left of the septum, and the knife pushed into the cavity until the point can be forced through the ventricular wall just below (ventricular side) the left auriculoventricular ring, and the ventricle-wall is then cut upward (as the heart is held) to the apex, in the line of greatest convexity, exposing the cavity of the left ventricle. The knife is laid aside and the ventricle is explored with the fingers of the right hand and the size of the mitral opening estimated. Before the fingers are introduced through the valvular openings the flaps should be carefully examined to see that no vegetations, thrombi, etc., are in danger of being loosened by them. With the opening of the heart-chambers the blood, if fluid, may pour out into the pericardial sac and flood the pleural cavity if not prevented by sponging or by removing it by means of a beaker. The knife is then introduced on the flat through the mitral opening into the left auricle in a line continuing the first incision with the junction of the left pulmonary veins. (See Fig. [38].) The knife is then turned with cutting-edge upward, the point thrust through the upper left pulmonary vein or between the left pulmonary veins, and the auricular wall is cut upward (downward anatomically) to meet the first incision below the mitral ring. The incision should pass between the mitral segments. The left auricle, mitral ring and flaps and the greater portion of the left ventricle are thus exposed and should be inspected.

Fig. 38.—Section of left ventricle and auricle, when heart is examined in the body. (After Nauwerck.)

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.

With the heart still lying flat in the pericardial sac, the aortic opening is explored by the index-finger of the right hand and the size of the ring estimated. The knife is then introduced on the flat, into the left ventricle, along the left side of the septum, through the aortic opening and as far as possible into the aorta. It is then turned, with the cutting edge upward, and the point pushed through the anterior wall of the aorta. The heart is then drawn downward and slightly raised by the left hand, holding it at the apex by the two flaps of the right ventricle. The knife is then drawn from above downward toward the apex, cutting in succession the anterior wall of the aorta, across the pulmonary artery, through the aortic ring, and the anterior wall of the left ventricle, just to the left side of the septum. By dissecting away the pulmonary artery from the aorta the incision through the former may be avoided. (See Fig. [41].) When desired this cut may be brought down through the septum instead, but if the bundle of His is to be studied in serial sections the cutting of the septum should be avoided. The enterotome or long straight shears may be used for all the incisions except the first ones made into the ventricles. For these the knife is necessary. The incision through the aortic ring usually cuts the anterior segment, but by making the cut more to the right the incision will pass between the anterior and the right posterior flaps.