SUMMARY AND CONCLUSIONS 1.A comparative anatomy of interventricular septal vascularization was studied on the normal hearts of 12 human beings, 80 dogs, 30 pigs, 25 calves, ten oxen, ten sheep and three horses for a total of 170 hearts. 2.The applied technique is described. This method of studying vascularization is simple, cheap, and specimens thus obtained, can be kept indefinitely. The present work was made possible by injection of vinyl acetate in the coronary vessels. The mold obtained by the corrosion technique gives a three-dimensional view of coronary vascularization. 3.Arterial vascularization of the interventricular septum in several different animal species may be classified in three groups. In a first group including man, pig and horse, vascularization was shared anteriorly by anterior septal arteries, collaterals of the anterior coronary artery, the latter being a branch of the left coronary also sharing vascularization, posteriorly, we find the posterior septal arteries, which are collaterals of the posterior coronary the latter is a branch of the right coronary artery. In man, the anterior septal arteries, are the important ones. In the equine species, the posterior septal arteries are preponderant. In porcine heart, anterior and posterior septal arteries share almost equally septal ventricular vascularization.A second group includes dog and sheep and in this group, the existence of at least one septal is shown, this being a branch of the left coronary and irrigates most of the septum. However, in dog, the septal is always more important than in sheep.In a third group, the bovine species was studied and it was demonstrated that there is a constant descending septal artery; this is a branch of the right coronary and supplies the superior medial third or two-thirds of the septum. The remainder of the septum is supplied by septal branches of the anterior and posterior arteries, which are issued from the left coronary artery.The septal artery was not found in dogs and horses. It was met one of 12 times in human hearts, its origin being the conus artery. The descending septal artery was also met in 18 of 30 porcine hearts, and two of ten hearts of the bovine species. 4.Venous vascularization of the septum generally closely follows the arteries to drain finally into the anterior and posterior interventricular veins, but this vascularization drains mostly into Thebesian veins. On our specimens, we rarely met a vein accompanying septal arteries on dog, sheep, calf and ox.