[The coelom and its lining as organoblastema]

Dissent in the description of the walls of the serous cavities in the thorax has led to an investigation of the origin of these serous walls in man. The macroscopical and microscopical observations in human dissected and sectioned material not only solved this contradiction, but also suggested, that the development of the coelom is a more complicated process than is presumed in the literature. On one side our observations are confirmed, on the other side they are contradicted. Therefore, we decided to follow the development of the coelom conscientiously, step by step. A pilot study of embryonic stages in the mouse pointed out that in this laboratory animal very similar processes take place, and that in very young stages the coelomic wall consists of epitheloid cells. Studying the behaviour of these epitheloid cells in embryonic stages in the rat, it appeared that the development of the coelom must not only be looked upon as an outgrowth and a modification of a cavity, but as an outgrowth and a modification of an organ, which consists of a cavity surrounded by its own specific wall. It is evident that the cells of this coelomic wall determine the outgrowth and the modification of this coelomic organ, which can be considered as a blastema for various organs in the thorax.