Abstract
Chief attention of this article is focused on the differentiation between PC-dependent “relaxing factor” (PC=Phosphocreatine), identified as creatine phospho-kinase by Lorand, and ATP-dependent one, similar to or identical with Marsh-factor. Results obtained by the present author proved that these two factors are quite different from each other. The present author is of opinion that creatine phosphokinase-PC-ATP system added form without has not a remarkable relaxing effect, if not aided by some other factors. The mechanism of contraction-relaxation cycle in muscle was discussed.
