The pattern of the microcirculatory bed in the ventricular myocardium of domestic mammals

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Abstract
Observations, as determined by injections of India ink through the coronary arteries of isolated and perfused beating hearts, were presented. Tissue blocks were removed from the right and left ventricular walls and the interventricular septum, sectioned and cleared for microscopic examination and photomicrography. The term microcirculatory bed was defined as those vessels 100 μ and smaller in diameter. The descriptions were based on 76 normal adult hearts of both sexes of six domestic species.The arterioles divided by dichotomous branching until the final division resulted in two daughter capillaries. At no time was a capillary observed leaving an arteriole larger than 15 μ in diameter. The arterioles had a modified type of end artery pattern. Arterial anastomoses were uncommon in the areas and species examined. A specific area of a cardiac muscle fascicle was supplied by several arterioles whose capillaries intermeshed. The implications of this concept in relation to micro‐embolism were explored.Capillary anastomoses were frequent but the connecting vessel was only about 20 μ in length. Three types of capillary anastomoses were identified. Capillaries did not cross the muscle fascicles of the myocardium.Collecting venules were often distinctive in their morphological pattern. “Turnip root” patterns were observed in all species and represented the local venous collection of a muscle fascicle. A venule's capillary components were usually from several arteriolar sources.Supported in part by research grant HE 04217‐05 from the National Heart Institute, U. S. Public Health Service.