Charles C Thomas • Publisher 



Bannerstone House 



301-327 East Lawrence Avenue, Springfield, Illinois 



Published simultaneously in the British Commonwealth oj Nations by 

 Blackwell Scientific Publications, Ltd., Oxford, England 



Published simultaneously in Canada by 

 The Ryerson Press. Toronto 



This monograph is protected by copyright. No 

 part of it may be reproduced in any manner 

 without written permission from the publisher. 



Copyright 1931, 1939, 1946, and 1954 by Charles C Thomas • Publisher 



First Edition, January, 1931 



Second Edition, September, 1939 



Third Edition, January, 1946 



Third Edition, Second Printing, November, 1947 



Third Edition, Third Printing, August, 1950 



Fourth Edition, September, 1954 



Library of Congress Catalog Card Number: 54-6567 



Printed in the United States oj America 



