Abstract
The periarterial Purkinje fibers in the right ventricle of adult and newly hatched chicks were investigated with the electron microscope. Fixation was carried out in glutaraldehyde, followed by osmication. 1) The fundamental strucure of the chick Purkinje fiber is identical with that of the mammalian heart. However, several modifications were observed, such as fine filaments distributed at random throughout the cytoplasm (which is considered the most conspicuous feature), poor granulations and relatively deformed mitochondria. 2) Cellular junctions in the chick Purkinje fibers are simpler than those found in the mammalian heart. The structure of the junction seems to be dependent largely upon the organization of the myofibrils in the adjoining cells. Associations were described between what is considered the distal end of the Purkinje fiber and the ordinary cardiac muscle cells. 3) The Purkinje fiber is considered not to be embryonic in nature, but to represent a pathway of development different from that of the ordinary cardiac muscle cells.
