PREFACE. 



VAEIOUS sides of the complex subject dealt with in this 

 volume are, from their very nature, more or less technical. 

 To bring it, as a whole, within the grasp of the general 

 educated public, great pains have been taken to present 

 the statements of facts and reasonings on the several 

 phases of the subject in a manner as simple as was pos- 

 sible that is, to free the discussion from all technicalities 

 which were not inherent in the subject itself. At the 

 same time, I have not lost sight of the probability that 

 such a book as this may possess some special interest for 

 a rapidly growing section of readers more or less familiar 

 with technical discussions on psychological subjects, as well 

 as for another (composed for the most part of members of 

 the medical profession) to whom anatomical and physio- 

 logical discussions are no less familiar. It would be 

 difficult indeed fully to satisfy the requirements of these 

 different classes of readers, especially within the compass 

 of one comparatively small volume ; still, I have striven to 

 make this work not unworthy of some consideration from 

 each of these classes, though always with principal regard 

 for the requirements of the larger body of general readers. 

 The fact of having to treat the subject thus briefly, al- 

 most of necessity compelled the omission of certain topics 

 of which one or other reader will perhaps expect to find 

 a discuoaiuii. The gaps, too, are, unfortunately, both 



