Abstract
1) The contents of cytochrome C and nucleic acids in the fresh muscle strips and the stored powders from various parts of the dog heart were determined.
2) The left heart in situ contains probably 19 mg. % of cytochrome C, 8mg. % of DNA-P and 20mg. % of RNA-P.
3) The puppie's hearts contain 1.4 times as much DNA and cyto-chrome C as that of adult dogs. The RNA contents are rapidly lost after death, and also are not differentiated between both groups.
4) Among the various parts of the dog heart, both RNA and cytochrome C are concentrated predominantly in the left heart, which contains comparatively smaller amounts of DNA and then may consist of much larger cells. The auricles, which consumes oxygen most actively, contain the least amount of cytochrome C.
5) During the maturation of the dog, the right heart of which the absolute content of cytochrome C is relatively small, synthesizes this enzyme increasingly, and in contrast the left heart apparently discontinues its synthesis.
