Dimensions of Blood Vessels from Distributing Artery to Collecting Vein

Measurements of lengths, diameters, and numbers of post-capillary vessels were made in the bat's wing. The cross-sectional area and capacity in the various portions of the vascular bed were calculated. The greatest total cross-sectional area in the entire vascular bed was found in the venules, a result not in agreement with similar reports made by others using measurements from vessels in fixed preparations. This discrepancy probably results from disagreement regarding the diameter of capillary vessels. Calculations to determine the per cent of total volume in each portion of the vascular bed showed that the venous system accounts for as much as 80% of the total vascular volume.