lO PREFACE TO THIRD EDITION 



these questions would spoil the unity of the work ; it 

 was necessary only to put, at the limits of my science, 

 sign-posts indicating the destination of the roads that 

 start from these points, and distinguishing the right 

 from the wrong way. For the rest, I believe that 

 my treatment of these various questions is not wholly 

 superficial, but sufficiently informs the reader on the 

 substance of them. I am confirmed in this by the 

 testimony of experts. 



I have to express my cordial thanks to my colleagues 

 for their friendly interest. 



CONRAD GUENTHER. 



Freiburg, le^th March, 1905. 



