VI PREFACE. 



the pupils will use the questions and that their teachers will 

 not. 



Before concluding, I must express my sincere thanks to 

 Miss Frances T. Bauman, who has given me the benefit of 

 her many years' experience as an eminently successful 

 teacher. She kindly read a large portion of the manuscript, 

 and gave me much advice of which I have been glad to 

 avail myself. I have also to acknowledge my indebtedness 

 to Mr. W. H. Howell, Fellow of the Johns Hopkins Uni- 

 versity, who has corrected most of the proof-sheets, and 

 prepared the index. 



H. NEWELL MARTIN. 



JOHNS HOPKINS UNIVERSITY, 

 August 10, 1883. 



PREFACE TO THE SECOND EDITION. 



THE second edition of this book differs from the first for 

 the most part only in verbal alterations or typographical 

 corrections. Chapter XXIII., however, is entirely new, 

 and deals in some detail with the important question of 

 the influence on health of alcohol and various narcotics. 



H. N. M. 



March 26, 1884. 



