[Single ventricle and malposition of the dorsal part of the interampullary septum. Experimental study on the chick embryo heart].

After the blood has passed through the atrioventricular orifice or orifices or the atrioventricular canal when present, it is distributed to the ventricular ampullae. This distribution depends on the position of the dorsal component or dorsal horn of the interampullary septum with respect to the atrioventricular canal. The position of dorsal horn seems itself to depend on unequal or differential growth of the basal part of the ventricular ampullae. This has been demonstrated by the results, selectively destroying myocardial tissues by cauterisation: "high" cauterisation of the dorsal side of the right ampulla leads to the formation of a single ventricle of the left type; "high" cauterisation of the left side of the left ampulla leads to the formation of a single ventricle right type. In the first case, the dorsal component remains too far to the right, and, in the second, too far to the left. This differential growth which is exaggerated in these cases, also occurs in normal development. The right ampulla seems to be dominant with respect to the left and is responsible for the normal position of the dorsal horn to the left of the right atrioventricular orifice.