In using Ag impregnation method modified by A. Weber the author found the interneural synapses in the cardiac plexuses consisting of free terminations such as rings, "boutons terminaux" or of metaterminal structures. The endings are always free and either pericellular or pericapsular. The synapses show cyclic modifications under normal conditions and they degenerate after section of the vagus nerve. There are also "neuroid" terminations at the nerve cells in the cardiac ganglia.