First Edition, August, 1923 



Second Edition, December, 1925 



Third Edition, January, 1930 



Fourth Edition, March, 1934 



Preprint of pages ix + 79 of Fifth Edition, October, 1938 



Fifth Edition, April, 1939 



Sixth Edition, January, 1948 



Seventh Edition, October, 1957 



COPYRIGHT ©, 1957 

 The Williams & Wilkins Company 



Made in United States of America 



Library of Congress 



Catalog Card Number 



57-11183 



COMPOSED AND PRINTED AT THE 



WAVERLY PRESS, INC. 



Mt. Royal and Guilford Aves. 



Baltimore 2, Md., U. S. A. 



