CARDIAC VEINS.
The proper veins of the heart form a sepa rate system of small extent, which communi cates with the right auricle of the heart by the great cardiac vein. Their principal trunks are thus distinguished : 1. Great cardiac vein (anterior or great co ronary vein). — This vein commences on the anterior surface of the heart, near its apex, and ascends in the anterior interventricular groove, as far as the base of the ventricles, where, bending abruptly to the left, it gains the back of the heart by passing round the left margin of the organ in the deep horizontal groove between the left auricle and the left ventricle. Still observing a transverse direc tion, the vein in its farther course, passes from left to right, crosses the upper extremity of the posterior interventricular and filially opens into the posterior surface of the right auricle to the right of the mesial line.
Before its termination, the great coronary vein presents a bulbous dilitation (sinus cf the coronary vein). Its orifice in the right auricle, which is protected by a special valve (valve of Thebesins or lesser Eustachian valve), is situated between the great Eustachian valve and the right auriculo venticular opening.
Posterior cardiac vein (posterior or lesser coronary vein).—The lesser cardiac vein arises near the apex of the heart, on its posterior surface, and ascends in the posterior interven tricular groove, where it is joined by muscular branches from either side. Finally, it ter minates in the great coronary vein when that vessel forms its ampulla in the deep groove above the base of the ventricles.
Several small veins, which belong exclu sively to the right ventricle, ascend along the right border of the heart, and, curving round in the groove between the right ventricle and right auricle, likewise join the great coronary vein — one of those which has long been dis tinguished by the name of the " vein of Galen," is stated to communicate, frequently, by a separate opening, with the right auricle.
Other veins of extreme minuteness (vents minima' or veins of Thebesius) are described as opening separately at various points into i either auricle. Their existence is denied by some anatomists.