The morphogenesis of the ventricular flow pathways in man.

This work which is based on the study of eight human embryos of 4,5 to 13,6 mm from the Madrid collection, and also on six plastic reconstructions made by the BORN method, and on experiments on chick embryos (ligature of the left vitelline vein in embryos, 3 days of incubation) enables us to reach the following conclusions: no true rotatiorial movements take place during normogensis. Only ventromedial rotation of the right ventricle is observed in stages 12 to 14. This rotation will place the right ventricle, and therefore the vestibulum pulmonalis in front of the aortic infundibulum. We consider that the initiation of cardiac septation is to a great extent due to hemodynamic. causes. During normogenesis in all cases, from the earliest stages of development the presumptive pulmonary outflow tract is always anterior and to the right of the presumptive aortic tract. We do not agree with the statement of GOOR and EDWARDS and VAN PRAAGH R. and VAN PRAAGH S. (1965), that in some stages the presumptive coni of the aorta and pulmonalis are arranged inversely to the way in which they will arranged later.