No particular difficulty was met in the demonstration of the atrioventricular node and bundel of His in the human heart when standard methods such as that described by RÉNON and GÉRAUDEL (posteriorly referred as MAHAIM's method) was followed. The figures here presented refer to a white female 36 years old, not infected by Schizotrypanum cruzi, whose heart was apparently normal, macro and microscopically. They will be useful for comparison with similar structures to be latter reported in patients with chronic Chagas's disease. Our results confirm the total absence of ganglion-cells and nerves in the atrioventricular node and bundle of His of the human heart as opposed to what is found in the ungulates as well as the continuity between muscular fibers of the left branch and ordinary muscle fibers, and the presence of Purkinjke fibers in the musculature of the left ventricle lying immediately beneath the left branch which renders sometimes difficult to demarcate such a structure. A comprehensive survey of the literature was given, and the text transcribed whenever if was felt that a translation would perhaps distort the real meaning of the author.