Excerpt from Memoirs of the Wistar Institute of Anatomy and Biology, Vol. 7: An Experimental Analysis of the Origin of Blood and Vascular Endothelium; The Origin of Blood and Vascular Endothelium in Embryos Without a Circulation of the Blood and in the Normal Embryo, Forty-Nine Figures; A Study of Wandering Mesenchymal Cells on ThAll of the vertebrate classes present these many questions of blood origin, etc., but the forms upon which this investiga tion has been conducted, the Teleosts, possess in addition many extremely interesting special problems. In all other meroblastic embryos the majority of the earliest blood cells arise in yolk-sac blood islands. Yet in many of the Teleosts there are apparently no early blood islands on the yolk, but all of the blood forming cells are contained within the embryonic body.This intra-embryonal blood anlage has been frequently de scribed by many authors as the intermediate cell mass. The intermediate cell mass as has been suggested by Marcus Mollier and others, is really the homologue of the blood forming yolk-sac mesoderm in the other meroblastic types.The bony fish is important as an object of study on account of the fact that so many of its organs and tissues arise in a way peculiar to the group and differing from the other vertebrate classes.

The solid gastrular invagination described by Sumner the original solid condition of the central nervous system, the solid optic knob which changes into the optic vesicle, and in the present connection, the very particularly interesting solid cord of cells, the intermediate cell mass, which is to give rise to the red blood corpuscles of the individual make the Teleosts a group of great embryological interest.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis 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.