Portions of auricular myocardium obtained surgically from a series of 11 cases of congenital and rheumatic heart disease were embedded for electronmicroscopic study. The normal distribution of the organelles in the ultrastructure of the human heart is described. The difference between human and other mammalian heart muscles appears to be only quantitative.
Stein AA, Thibodeau F, Stranahan A. III. Electron Microscopic Studies of Human Myocardium. JAMA. 1962;182(5):537-540. doi:10.1001/jama.1962.03050440029009