Abstract
The general principles of measurement of microscopic figures by projectometric methods have been treated in another communication, 1 and applications to the measurement of islands of Langerhans in the pancreas have been presented. 2 ,3 The greatest difficulty in this work was due to the enormous variations in their volume and shape. Since this difficulty was far less evident in the case of the glomeruli of the kidney an investigation of this field seemed indicated, and we wish to give at present some of the results so far obtained.
It has been thought preferable to make estimates free from the assumption of spherical form for glomeruli wherever possible, but to use this to furnish an independent check. However, in the material used, it was found that areas of glomerular particles in sections (7 micra thick) could be approximated satisfactorily by comparison of their projected images with circles of known size; and this was done rather than trace and measure them with a planimeter. A glomerulus was considered to belong (in the sense previously 1 defined for islets) to a given section if its greatest cross-sectional area lie therein. Thus it was possible from random samples and assumption of approximate spherical form to estimate directly mean volume and diameter of glomeruli in a given region. However, we are interested in data more comprehensive than this, and, if possible, free from the assumption of sphericality; e. g., total glomerular tissue volume (Is) in the sample region. Previous attempts in this direction have been based upon treatment as if the section were opaque, i. e., attempting to measure all areas of glomerular (or islet) tissue in the first presented surface; but it is much easier in practice to focus upon the greatest cross-sectional area in the section of each glomerular particle.
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