抄録
An examination was made of the distribution of cardiac musculature in the pulmonary venous wall of three Mustela species (ermine, American mink and ferret) of different body size. Only the ermine possessed cardiac myocytes in the tunica media of the intrapulmonary venous walls continuing from the left atrium, whereas the two other species had the musculature restricted to the large extrapulmonary vein. The distribution of the musculature is thought to depend on the body weight and heart rate of various species. These findings confirm the supposition that, whereas smaller mammals have more extensive cardiac musculature, even in the intrapulmonary venous wall, in order to regulate venous blood return and to resist reflux resulting from frequent atrial systole, the larger species may not require cardiac musculature in the distal vein.
