PREFACE IX 



and for permission to use certain of the figures and illustrations, to the 

 various authors and publishers who granted it. For the excellent man- 

 agement and careful execution of the presswork, the author wishes to 

 thank the publishers, whose courteous and friendly dealings have always 

 made the work easier. 



J. J. R. MACLEOD. 



University of Toronto, 

 Toronto, Canada. 



