Nerve Fibrils in the Sino-auricular Node

Aside from the nerve fibers which enter the pace-making node from the subepicardium, there were observed within the limits of the node a few ganglionic cells and a plexus of moniliform nerve fibrils in very close relation to its muscle fibers, hence the sino-auricular node, like the auriculo-ventricular, may be considered from a histological standpoint a neuromuscular organ.