[Ultrastructure of the cardiomyocytes of the pedicles of the bundle of His in the rat heart].

Light optic and electron microscopic investigation on composition and geometry of His' bundle branching in the upper part of the intraventricular septum was made. Branching of both peduncles of the atrioventricular (AV) bundle were demonstrated to be represented by a single cell type, its ultrastructure was described. Possibility to apply different ultrastructural criteria in order to determine this (III) type of cells in the conducting system of the heart was discussed.