1. Therty-three adult male rabbits were used for this experiment. The animals were divided into four groups. In the first experimental group, a piece of its own spleenic tissue was implanted to the myocardial surface in each animal after the internal mammary arteries had been ligated bilaterally. Within one to four weeks after the first operation, the animals were subjected to ligation of the circumflex branch of the left coronary artery. Out of 18 animals, 12 survived over 5 days after 2nd operation. In the second experimental group the same procedure was repeated as group 1, except the implantation of the spleenic tissue. Two animals survived out of 5 operated. In the control groups (the 3rd and 4th groups) no operation was performed before ligation of the branches of the coronary artery. In the 3rd group, after the ligation of the ant. descending branch, 3 out 4 animals survived over 5 days, while in the 4th group, after ligation of circumflex branch none survived over 5 days in 6 animals operated. 2. In group 2, X-ray photographs indicate that collateral circulation was established through the anastomosis between pericardial vessels and branches of the coronary artery. 3. The X-ray photographs of the experimental group 1 proved the establishment of collateral circulation between ant. descending branch and circumflex branch of the left coronary artery by the vasculature in the spleenic implantation. 4. As is shown by periodic acid Schiff reaction, (1) in both control groups, the glycogen granules in the area of coronary occlusion were more reduced than in the border area, (2) in the second experimental group the glycogen granules in the area of coronary occlusion have slightly increased in comparison with those in same area in the control group and (3) in the first experimental group the glycogen granules in the area of coronary occlusion were increased more than in the same area in the second group. These changes offer convincing elucidation that in the first and second groups, owing to the production of the intercoronary collateral circulation or the hemodynamic effect, the blood supply to the area of the coronary occlusion was ificreased.