I. The Lobe of the Azygos Vein Lorus venae azygos, a now commonly recognized malformation of the right upper lobe, was first described in 1777 by Heinrich August Wrisberg, Doctor of Medicine and Director of the Anatomical Institute at Gottingen (25). His “observations,” made on a cadaver of a three-year-old boy, were especially noteworthy in recognizing that the vena azygos of this specimen presented an aberrant configuration on both sides. The original wood cut (see Fig. 1) shows only the right lung, but the description of the vein of the left side leaves no doubt that the left upper lobe was also cleft: “In order that the progress of the left vena azygos towards the subclavian (i.e., the innominate vein) might be rendered easier, the superior lobe of the left lung was provided with a comparable sulcus or rather incisure such as we have described in connection with the right vena azygos.” Although this left-sided anomaly has never been reported again in a dissected specimen, Schmitz-Cliever (22) by employing laminagraphy has identified a left pleural septum in a girl of twenty-two. This descended vertically from the apex of the left lung to enclose a vessel at its lower end. He reports at least two other cases in the literature which he recognizes as authentic. Wrisberg's account of the right side describes the vena azygos as undergoing “a marked bend in the interval between the heads of the third and fourth ribs,” as being “directed toward the interior at less than a right angle,” as entering “a sulcus in the superior lobe of the right lung prepared in a manner for transmitting the azygos vein,” and as finally “descending into the beginning of the vena cava”; but he failed to note the pleural septum. Discovery of this, according to Collins (12), awaited the publication of Rokitansky's Pathologische Anatomie in 1842–46.2 Eight decades later Velde (24) identified the pleural septum in chest plates. Schmitz-Cliever estimates that the septum occurs in 0.3 per cent of all x-rayed lungs. Clive (11) found it in 0.11 per cent of 30,000 W. A. A. F. recruits. Mäusert, however, in a Dissertation of 1899, quoted by Bluntschli (2) notes that Prof. Boström “found 17 azygos lobes in 1,600 dissections” —among them a thoracopagus with bilateral lobes of the azygos vein. Perhaps, the lesser incidence in chest plates may be explained by the difficulty of seeing the “hair-line mesentery” in those cases in which it lies nearest to the spine. 1. The Mesoazygos: The recent finding of an azygos lobe in a dissecting-room cadaver—our first in some 500 specimens—has made it possible to clear up many obscure points regarding the anatomy of this anomalous pleural mesentery.
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Jan 1, 1954
J C T Oates 
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