Author : Wistar Institute of Anatomy and Biology
Publisher :
ISBN 13 : 9781330603826
Total Pages : 550 pages
Book Rating : 4.6/5 (38 download)
Book Synopsis Journal of Comparative Neurology, 1921, Vol. 33 (Classic Reprint) by : Wistar Institute of Anatomy and Biology
Download or read book Journal of Comparative Neurology, 1921, Vol. 33 (Classic Reprint) written by Wistar Institute of Anatomy and Biology and published by . This book was released on 2015-09-27 with total page 550 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excerpt from Journal of Comparative Neurology, 1921, Vol. 33 Only a relatively small portion of the neural crest in the head is involved in the formation of cerebral ganglia. In the urodeles the neural crest forms in the anterior head region an almost continuous sheet of mesenchyme, lying lateral to the axial mesoderm which is derived from the endoderm, and is interrupted for a time by the olfactory bulb and optic stalks only. In the region of the mandibular and branchial bars, the neural crest migrates ventrally into these bars to the extreme ventral level of the body and is prevented from forming a junction with the crest of the opposite side by the presence of the heart and ventral aorta. The possibility of determining the fate of neural crest cells that do not enter into the composition of cerebral ganglia depends upon conditions that exist in some types and are apparently absent in others. It is the almost unanimous opinion of workers that it is extremely difficult and often impossible to determine the fate of all neural crest cells in the anterior head region. In the branchial region of the lower vertebrates particularly, the situation is very different. A number of reliable workers have given detailed descriptions of the fate of the neural crest cells and of the manner in which they enter into the composition of structures usually considered as mesodermal in origin. As to the migration of the neural crest beyond ganglion-forming regions in all vertebrates, there is apparently little doubt. In the urodeles the determination of the extent of the migration of the neural crest and the differentiation of the neural crest and its derivatives from those of the endoderm are comparatively easy except in the anterior region. The contrast between the large, heavily yolk-laden, light staining endoderm cells and their derivatives on one hand and the smaller, dark staining, pigmented, slightly yolk-laden ectoderm cells and their derivatives on the other hand is very striking. In addition to these distinctions based upon size of cells, staining reaction, pigmentation, and number of granules, there is also an actual difference in the size of yolk granules carried by endoderm cells as compared with those carried by ectoderm cells, those carried by endoderm cells being larger. 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.
