In Part 1. the author investigatad the effects of the unsaturated fatty acid fraction extracted from the rabbit liver after x-ray irradiation on the succinic dehydrogenase system in Ehrlich ascites tumor cells and in the normal rabbit liver, and it was concluded that although this fraction does not greatly affect the normal liver cells, at a higher concentration it seems to induce cell degeneration which in turn results in a decrease in the respiratory enzyme activity. In the present experiment the author studied the morphological changes brought about by this substance in Ehrlich ascites tumor cell and the in vivo changes induced by it in the succinic dehydrogenase system. In conducting this experiment the results obtained by Yamamoto et al. of our department were referred to. With respect to the morphological changes in the tumor cells, it was observed that this substance acting for a short period of time will accelerate the respiratory enzyme activity transiently while when acting for a longer period, it decreases the activity. These findings agree more or less well with the results in Part 1. Even in the in vivo reactions the respiratory enzyme activity in the tumor cells is elevated temporarily and when acting for a longer period of time this substance decreases the activity. From these findings it is concluded that this substance does elevate the respiratory enzyme activity transiently but when it acts for a longer period of time, it seems to bring about a fall in the activity and further acting directly on the respiratory enzymes it induces the disorder in respiration.