Xv PREFACE TO THE FOURTH EDITION. 



now offers the more matured fruits of his inquiries and reflections, with 

 some confidence that, even if his views should hereafter require modifi- 

 cation as to details, they will be found to be fundamentally correct, and 

 to furnish materials of some value in Psychological inquiry, as well as 

 in the study of Mental Pathology, a subject which is now receiving for 

 the first time (in this country, at least) the attention which its vast im- 

 portance demands. The peculiar states which are known under the 

 designations of Somnambulism, Hypnotism, Mesmerism, Electro-Biology, 

 &c., are all considered in their relations, to Sleep on the one hand, and 

 to the ordinary condition of Mental Activity on the other ; and the 

 Author ventures to believe that he has not only succeeded in throwing 

 considerable light upon the nature of these aberrant forms of psychical 

 action, but that he has been enabled to deduce from their phenomena 

 some inferences of great importance in Psychological science. He 

 would particularly refer to all that portion of Section 5 (" On the Cere- 

 brum and its Functions") which relates to the Automatic operations of 

 the Mind, and to the relation of the Will to these, as opening up what 

 he believes to be an entirely new line of inquiry. 



It is with great satisfaction that he can refer to his friends, Dr. Hol- 

 land and Dr. Laycock, as participating (in regard to all essential points 

 at least) in his own views on all these subjects ; and though all which 

 he has here written upon them is the expression of the results of his 

 own observation and reflection, yet he gladly takes this opportunity of 

 acknowledging the great benefit which he has derived from the writings 

 and conversation of these philosophical and independent thinkers. It 

 would be ungrateful if he were not also to record his obligations to his 

 friendj, Mr. John S. Mill, and Mr. Daniel Morell, who have allowed him 

 to bring his Psychological views under their notice, from time to time, 

 and to subject them to the test of their own far more extensive and 

 profound acquaintance with that department of his inquiry. 



In Chapter XV., " On Sensation, and the Organs of the Senses," 

 comparatively little change has been made; several additions have been 

 introduced, however, and some corrections made. The next Chapter 

 (xvi.), " On Muscular Movements," has been entirely remodelled, the 

 portion which relates to the vital endowments of Muscular Fibre having 

 been removed to Chapter V., Section 6, and its place supplied by new 

 matter which contains many original views, especially under Section 4, 

 which treats of "the Influence of Expectant Attention on Muscular 

 Movements." Comparatively little alteration has been found necessary 

 in Chapter xvil., " On the Voice and Speech," or in Chapter xvili., 

 " On the Influence of the Nervous System on the Organic Functions ;" 

 an important addition has been made to the latter, however, with refer- 



