TO THE READER. vii 



should do his utmost to make the conclusions at 

 which he arrives intelligible, without affectation of 

 learning, without mystery, and without in any way 

 exaggerating the importance of what he may have 

 to communicate. For the public may reasonably 

 desire some calm statement of proved facts in a matter 

 of such importance. It should be the writer's en- 

 deavour to tell his story simply, so that those who 

 wish may learn, and to take pains to make the facts 

 as clear to other minds as they appear to his own, 

 without trying to amaze by calling in the aid of 

 startling similes and striking illustrations which but 

 too often divert the attention from the real matter 

 under consideration, and are calculated to distract 

 the mind and prejudice the judgment. 



In this edition I have introduced a new section on 

 the Mind. The views now published in a connected 

 form for the first time, were put forth in my lectures 

 delivered by direction of the .Radcliffe Trustees, at 

 Oxford during the Michaelmas term of last year, 

 reported in the " Medical Times " and " Gazette," and 

 less systematically in my physiological lectures de- 

 livered at King's College, London, during the winter 

 sessions 1863 to 1869. 



6 1 , Grosvenor Street ; 

 Christmas, 1869. 



