[Experimental study of the gastric organogenesis of the Rabbit foetus : Normal development. Experimental localization of the presumptive area. Development of the cultured and grafted stomach].

1) An ultrastructural and optical examination of the "in utero" development of the stomach in Rabbit embryos, demonstrates that the epithelium increases by"vacuolisation". The intraepithelial vacuoles, formed by a secretory process, secondarily open into the gastric cavity, whence the constitution of primary villi. Then the mesenchyme buds chorionic evaginations under the epithelial crests and transforms the primary into secondary villi. As the villi grow longer the epithelium loses its pseudostratified structure in order to become simply unistratified. At the same time, the four types of gastric cells progressively accomplish their differentiation into parietal, mucous, peptic cells and surface epithelium. 2) The presumptive gastric area of a ten-day-old Rabbit embryo corresponds to the lower third of the entomesoblastic part of the embryonic pharynx, posteriorly amputated at the umbilical edge. This presumptive area, grafted in the Chick embryo, differentiates into characteristic gastric tissue. Finally the stomach is explanted ("in vitro" and"in ovo") at different stages of ontogenesis. Up to the thirteenth day it degenerates in culture but grows and accomplishes its morphogenesis as a graft. From the fifteenth day, the cultured and grafted stomach differentiates on both morphogenetic and cytochemical planes.