A right, or anterior, and a left, or posterior, coronary from their point of origin, turn in a ventral direction between the root of the aorta and the pulmonary artery, the right going to the right coronary groove and the left to the left coronary groove in the crown furrow. From here they send branches into the heart. The anterior, right, coronary, or coronaria dextra, the larger, is given off from the inferior wall of the aorta. It divides into a ramus superficialis and a ramus profundus. The ramus superficialis enters the crown furrow and divides into two or three branches on the right heart wall. These branches extend to the apex of the heart. Twigs from this artery along its course extend into the muscular wall reaching the posterior of the coronary groove where they anastomose with those of the left coronary, the ramus profundus, and with other branches from the same artery. The ramus profundus, larger than the preceding, gives off fine branches into the walls of the aorta and of the pulmonary artery, then enters from behind into the right wall of the septum ventriculorum, extends into the apex of the heart, and supplies the septum, or right inner chamber wall with the last branch, this breaking through the posterior wall of the auricular appendage. The posterior, _left coronary_, or _coronaria sinistra_, originates from the dorsal wall of the aorta, proceeds as one branch on the upper surface of the left auricular appendix, and then extends between the left appendix and the pulmonary artery to the ventral surface of the heart. On the left side it supplies the wall of the pulmonary artery and gives off a ramus profundus. It sometimes divides into two parts and supplies the ventral wall of the right chamber and then extends to the left wall of the septum medium. The rest of the coronaria sinistra enters into the left crown furrow as the ramus superficialis, which provides the left and dorsal upper surface of the left chamber to the apex. From this furrow it extends into the left chamber and the left appendage, and finally fuses with the ramus superficialis of the coronaria dextra. THE BLOOD-VESSELS The blood-vessels consist of arteries, veins and capillaries.