Maude Abbott Lecture--1991. The capillary then and now: an overview of capillary pathology.

The concept of capillary is traced through its historical development, beginning with the pathologic "synanastomoses" between arteries and veins as proposed by the ancient Greeks. Harvey assumed that arteriovenous connections existed but never saw them. Malpighi and van Leeuwenhoek were the first to observe the capillary circulation in vivo. In the 1800s, pathologists contributed two advances: a method for proving that capillaries have a structured wall (von Recklinghausen) and the notion of "capillary leakage" in inflammation (Cohnheim). Then physiologists took over for half a century (Starling, Krogh, Pappenheimer) until electron microscopy created a new viewpoint (Palade). Several topics of capillary pathophysiology are discussed: vascular labeling and the capillary as a privileged vessel; capillary versus venular leakage in inflammation; endothelial tone. The overview concludes with a summary of 15 pathologic events that may occur in capillaries.