Some observations on the anatomy of the heart of the African lung fish,Protopterus aethiopicus Heckel

The heart of the dipnoanProtopterus aethiopicus structurally resembles that of the amphibians, but its conducting system is typically piscine. The sinus venosus is thick-walled and single chambered. The atrium, the ventricle and the conus are incompletely divided, each into two parts. A single atrioventricular plug of fibrocartilagenous consistency guards the atrioventricular opening. No ventriculoconus valves are present. Ganglion cells and nerves are present on the walls of the different chambers of the heart especially at the junctional sites. Since specialized conducting tissues or cells are absent, the cardiac muscles and nerves appear to be responsible for the conduction of impulse which have their origin in the sinus venosus.