Book - A Text-book of Embryology

A TEXT-BOOK

OF

EMBRYOLOGY

FOR STUDENTS OF MEDICINE

BY

John Clement Heisler, M.D.

(1907)

PREFACE TO THIRD EDITION

The great activity along the lines of embrvological research during the past half-dozen years has brought forth much literature and some new facts. In some cases existing views have thereby been modified or set aside; in others, they have been more firmly established. In presenting the third edition of this book the effort has been made so to revise the text as to harmonize it with the results of recent researches. To this end, certain of the sections have been practically rewritten, while others have been slightly altered, and still others have been merely somewhat amplified. Where changes have been made the authorities therefor have usually been cited. The revised portions of the book include the sections dealing with the ovum, the spermatozoon, the blastodermic vesicle, the amnion, the vascular system, the pancreas, the spleen, the larynx, the thymus, the thyroid, the parathyroid, the adrenal, the kidney, the spinal cord, the vitreous, the musculature, and the vertebral column.

J. C. H.

3829 Walnut St., Philadelphia, March, 1907.

PREFACE

The facts of embryology having acquired in recent years such great interest in connection with the teaching and with the proper comprehension of human anatomy, it is of first importance to the student of medicine that a concise and yet sufficiently full text-book upon the subject be available. It was with the aim of presenting such a book that this volume was written, the author, in his experience as a teacher of anatomy, having been impressed with the fact that students were seriously handicapj>ed in their study of the subject of embryology by the lack of a text-book full enough to be intelligible, and yet without that minuteness of detail which characterizes the larger treatises, and which so often serves only to confuse and discourage the beginner.

In the arrangement of the subject-matter of the book, it has been the aim not only to present a connected story of human development, but also to make each chapter as nearly as possible complete in itself, for the sake of convenience of reference. It is for this reason that some repetitions occur in the text. The frequent allusions to certain facts of comparative embryology are rendered necessary by the very nature of the subject, but it has been the writer's aim to make these allusions as simple and as easily intelligible as possible.

In the selection of the illustrations, great care has been exercised to employ those of the greatest teaching value, and to arrange them, with reference to any one chapter, as nearly as possible in proper chronological sequence. Due acknowledgement is made in each case for every illustration borrowed from other works.

With few exceptions, no attempt has been made to cite authorities in the text, and the author would here express his obligations to the writings of His, O. Hertwig, Kolliker, Schultze, Bonnet, Balfour, Marshall, Piersol, Minot, Tourneux, and many others.

J. C. H.

3829 Walnut St., Philadelphia,