Excerpt from Saint Louis Clinical Record, 1880-1881, Vol. 7: An Independent Journal of Medicine and Surgery The changes of the hypoblast are by far the Simplest of the germ layer metamor phoses. Its epithelial expanse becomes concave, with the concavity downward, and finallygit closes to form a tube, the 'primi tive visceral canal.* Around it the sero parietal lamella of the mesoblast forms an outer tunic, from which the sub-mucous, muscular and serous layers develop, the hypoblast contributes solely the epithelial tissues of the visceral canal and its diver ticula. This primitive visceral canal, which is at first straight and perfectly axial, has no oral or anal opening and terminates blindly at the cephalic and caudal ends of the embryo. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.