x ii PREFACE. 



useful as an introduction to the subject; but, as any 

 interest which attaches to it must be mainly his- 

 torical, I have thought it right to leave the essays 

 untouched. The history of the long controversy 

 about the structure of the brain, following upon 

 the second dissertation, in the original edition, 

 however, is omitted. The verdict of science has 

 long been pronounced upon the questions at issue; 

 and no good purpose can be served by preserving 

 the memory of the details of the suit. 



In many passages, the reader who is acquainted 

 with the present state of science, will observe much 

 room for addition; but, in all cases, the supple- 

 ments required, are, I believe, either indifferent to 

 the argument or would strengthen it. 



