[Presence in the heart of Protopterus annectens (Fishes, Dipneuste) of nodal and conducting cells histologically distinct from common myocardial cells].

Contrary to Francis and Davies's assumption according to which the impulse-conducting system of the Homoiothermal Vertebrates is a neomorphic structure, we have been able to identify in the heart of a Poikilothermal (Protopterus) impulse-conducting cells which possess distinctive histological characters.