Cardiac Rate and Rhythm

In the denervated state the mammalian heart, both in vivo and in vitro, is excited at very regular intervals, the coefficient of variance of the interbeat intervals not exceeding 2%. The pacemaker that is the source of this regular ex­ citation is localised normally within the sinus node (" sino-atrial node " node of Keith and Flack), a most intriguing small piece of tissue in the caval corner of ...