The structure of the lung

Abstract

THE difficulty in unraveling the various subdivisions of the bronchus of higher animals has made it impossible for us to gain a clear idea of the structure of the lung tissue. From a comparative standpoint it has also been impossible to gain light regarding the structure of the mammalian lung, mainly on account of the many variations in the different groups of animals. With these facts in view, I have attempted to rework the whole subject in question, guided by Dr. Mall and aided by a Fellowship granted by Clark University. I am also under obligations to Dr. Baur for most of the specimens of reptilian lungs.Microscopic anatomy has told us that organs are built up of like component parts, and that when the structure of one of these parts is known, the structure of the whole organ is clear. Yet it is necessary to homologize these parts in different animals, and this has been one of my problems. In order to do this we naturally inquire into the evolution as well as into the development of the different lungs. When studied from these standpoints, the structure of the lungs becomes quite a simple affair, provided we employ methods to unravel the more complex lungs. This is made possible by the employment of the more recent methods of reconstruction, which were introduced by His, by Born and many others in embryology, and by Mall,l Spalteholtz and myself in histology.The following methods were found to be of greatest value : I . Injecting the lung with air or illuminating gas and then 2. Corrosion preparation in wax or in Wood's metal.

Longitudinal distribution of vascular resistance in the pulmonary arteries, capillaries, and veins

“…The resistance to blood flow in the large conducting arteries and veins is not known, but an estimate can be made of the pressure drop across these vessels by using Poiseuille's law. Values for main pulmonary, artery, left pulmonary artery, and venous trunk diameter were taken from the measurements of Miller (18), and values for vessel length from the estimates of Schleier (1). At the average flow in our experiments the pressure drop across the main pulmonary artery would be 0.08 cm H2O and the pressure drop across the left pulmonary artery would be 0.12 cm H2O.…”

“…Schleier made a detailed mathematical analysis of the distribution of vascular resistance in the human lung using Poiseuille's law. He employed Miller's measurements of vessel diameter (18) and assumed figures for vessel length in his calculations. He concluded that, in contrast to the systemic vascular bed where the muscular arterioles are the major resistance vessels, in the lung the capillaries are the major-site of vascular resistance.…”

Lung Circulation Modeling: Status and Prospect

“…11. 6,72,73,75,76 Recently, Burrowes et al 77 have begun to merge measurements providing detailed descriptions of the geometry of the large vessels obtained from volumetric CT, with statistically based models of the small-scale vascular structure. These studies have contributed significantly to the understanding of the flow distribution within the pulmonary circulation.…”

Fluctuations, Noise and Scaling in the Cardio-Pulmonary System

“…Morphometric data have generally been obtained from plastic corrosion casts [60,63,66,67,68,76,79,82], and data obtained using imaging methods are becoming available [62,70,75]. The data consist of measurements of diameters lengths and numbers of vessels, and are commonly summarized by binning according to some ordering scheme [4,66,68].…”

“…Human [67] Human [66] Dog [76] Dog [63] Cat [82] Rat [68] For a symmetrical bifurcating tree, B = 2; B increases above 2 as the tree becomes more asymmetrical [4]. Values of B obtainable from the pulmonary arterial morphmetric literature are also presented in Table 1.…”