Résumé
The morphogenesis of the heart and the formation of the epicardium were studied with SEM, TEM and light microscopy. The results are as follows:1. There are two stages in the development of chicken heart: First is the formation of cardiac loop. In certain places, the sulcus appears outside, and the cresta appears inside during this stage. The formation of the cardiac loop indicates the establishment of the anlagen of the heart; Second is the differentiation of the anlagen, including the septation of the heart and the shift of each part of the heart. The shift of the atrium and the conus results from the shift of the right and left ventriculum. 2. The epicardium is not differcntiatcd from the myocardium, but formed from the mesenchymal cells which proliferate in front of the sinus venosus. These cells migrate and cover the entire surface of the myocardium.
Résumé
The development of the endocardial cushion and the ventricular septum of chicken heart was studied with SEM, TEM, light microscopy and histochemical methods. The results are as follows:1. The development of endocardial cushion begins from the proliferation of the endothelial cells which form cushion cells when these cells enter the cardiac jelly. Cushion cells also proceed mitosis and migrate toward the myocardium, and the endothelial cells cease proliferation when the reserve layers of cushion cells were formed. The fused endocardial cushion participates in the formation of atrioventricular orifice, the right tubercle prolongs toward the ventricular septum and eventually fuses with it.2. The cardiac jelly of endocardial cushion contains a great deal of hyaluronic acid which arranges in "trails", pioneering cushion cells migrate along the "trails" and change the component and arrangement of the matrix.3. Muscular ventricular septum is formed by aggregation of trabeculae inside the interventricular sulcus. The dorsal part of the ventricular septum fuses with the lower part of right tubercle of endocardial cushion and the ventral part fuses with the conus septum.