ee ee ee a 
PREFACE TO THE SIXTH EDITION ix 
and to Asst. Professor H. L. Reed of the Massachusetts College 
of Pharmacy who contributed the prints from which Figs. 138, 
139 and 140 were prepared. 
Finally, the author wishes to express his appreciation to 
P. Blakiston’s Son & Co. Inc. for doing its utmost in producing an 
attractive and well bound book. 
HEBER W. YOUNGKEN. 
Bosron, Mass., 
June, 1938. 
