Some Clinical Aspects of Accessory Lobes of the Human Lungs *

Until quite recently accessory lobes of the human lungs have been of but little interest except to the anatomist. To the clinician they were an unknown quantity. The X-ray has been disclosing them without their presence being appreciated. For years an unusual, fine, curved, linear shadow was noted very occasionally in the upper right-lung field, extending from the apex to a point near the mediastinum not far from the level of the second costal cartilage. When supposed to be due to a cause other than pleurisy, that cause was only here and there suspected as being an anomalous fissure separating the so-called azygos lobe, first described by Wrisberg in 1778. It remained for Bendick and Wessler, in 1928, definitely to establish the fact through autopsies of two patients-one a child, the other an adult-in whom the shadow was present. Since then numerous articles regarding this lobe have been published here and abroad, and the shadow is now familiar to all who make a study of roentgenography of the lungs. The size of the lobe varies considerably, as does, therefore, the location of the fissure shadow. At times the thin line lies close to the mediastinum, or again its convexity may be found relatively far out, even in the first interspace. There may or may not be a slight triangular density at the point where the linear shadow begins at the apex. Also, at times, one finds a slight uniform density over the azygos lobe as visualized mesial to the fissure line. The azygos lobe itself is a portion of the upper lobe cut off by the persistence of the fetal position of the azygos vein, which in fetal life lies lateral to the spine. The vein, therefore, traverses the substance of the upper lobe, lying in an infolding of the parietal pleura. For a time some held that the fissure was visible only when the seat of a pachypleuritis, but this assumption was disproved by its visibility in children with negative tuberculin tests and by its occurrence in individuals in whom there was no reason whatever to sus-