Chapters on mental physiology

Preface

TO

THE SECOND EDITION.

Another edition of this volume being required, - I have availed myself of the opportunity of making various additions and alterations, derived in part from further thought on these subjects ; in part from the progress of physical knowledge during the intervening time. I may mention, however, that I have found no cause to alter any of the general views propounded in these papers. Nor have I thought it right, by any fresh hypothesis, or more ambiguous language, to seek exemption from the charge of having stated difficulties, without resolving them. These difficulties do actually exist ; and it is better for the interests of truth and science that they should neither be disguised nor qualified. In the case of those

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VI PREFACE TO THE SECOND EDITION.

which are not in their nature insuperable, I have everywhere endeavoured, as far as lay in my power, to suggest the direction and method of pursuit best fitted for overcoming them.

Though these chapters are far from being offered as a complete treatise on Mental Physiology, yet I am willing to believe that the particular topics they embrace, as well as the method of treating them, with constant reference to that law of continuity which pervades every part of creation, may serve to elucidate many points not coming directly under review.

In further reference to this object, and for the better connexion of the whole, I have made a slight change in the order of the chapters ; placing first in the volume those which relate to the phenomena of Sleep, Dreaming, &c. It is the place fitly appropriate to a function which occupies nearly a third part of human existence ; and which, considered under the view I have especially sought to enforce, illustrates more variously and strikingly than any other, every part of Mental Physiology.

London : May, 1858.

PREFACE

THE FIKST EDITION.

Some explanation is necessary of the title and plan of this volume, that the reader may rightly apprehend not only the objects proposed, but also the method adopted to fulfil them.

The title will be understood as expressing that particular part of Human Physiology which comprises the reciprocal actions and relations of mental and bodily phenomena, as they make up the totality of life. I need not dwell on the great interest of this subject. It is attested, as every part of this volume will show, not solely by the natural and healthy conditions of existence, but even more remarkably by those of disorder and disease. Scarcely can we name a morbid affection of body in which some feeling

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Vlll PREFACE TO or function of mind is not concurrently engaged — directly or indirectly — as cause or as effect. No physician can rightly fulfil his duties without an adequate knowledge of, and constant regard to, these important relations.

I have adopted the title of Chapters on Physiology ; partly to avoid the profession of a complete treatise, which this is not; — partly to indicate that most of these topics, and even their titles, are taken from another work, the first edition of which was published thirteen years ago. Those who may have read my "Medical Notes and Reflections," will perhaps recollect such Chapters, as occurring in different parts of a volume chiefly devoted to subjects more strictly medical in character. Thus interposed, however, among the latter, they were deficient in the sequence and connexion naturally belonging to the topics they treat of; and which may be considered almost indispensable to a thorough understanding of the subject.

This deficiency I have sought to supply in the present volume by bringing these several Chapters into one series ; and by adding others which have appeared necessary to the completion of

THE FIRST EDITION. IX

the plan proposed.* While preserving the titles of those derived from my former work, and fol-

* These new chapters were originally intended for a second volume of my former work ; but I have thought it better to place them here, as well from their close connexion with the other subjects treated of, as also from a doubt I entertain as to the publication of a second volume in the same form as the first. Though happily there are many reasons justifying the hope that this work has been useful to the profession, yet I am led to consider it as a fault in the original plan, that the subjects are too numerous, and too little connected in series, for that ready reference, which it is important both for the author and his readers to obtain.

A few words more I may be permitted to add regarding this former work. In selecting the subjects for it, I chose those especially which, as involving general relations, not perhaps sufficiently regarded, seemed best adapted to suggest new views as to the causes, character, and treatment of disease. In the discussion of the subjects so chosen, the plan of the volume limited me to certain general principles and outlines of inquiry. But I still entertain the hope that some of these topics may be more fully examined by other writers ; and under this view I venture to suggest a few of the Chapters, which seem especially to admit of such larger discussion. I would name the following : " On Hereditary Diseases ; " " On Morbid Actions of Intermittent Kind ; " "On the Connexion of certain Diseases;" "On Diseases commonly occurring but once in Life;" "On the Influence of Weather in relation to Disease ;" " On disturbed Balance of Circulation and Metastasis of Disease." And to these I would willingly add (though I have myself applied the hypothesis only to the Indian Cholera) the general question regarding the Influence of Organic Matter in the atmosphere as a cause of disease — a subject which I feel assured will hereafter gain greatly in importance, and illustrate many points in pathology, hitherto unexplained or obscure.

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lowing the same general train of reasoning to the same conclusions in each, I must mention that they have been almost wholly rewritten, and very materially enlarged ; such alterations and additions being made necessary, partly for the connexion of the subjects thus brought into closer association ; principally from the recent accessions of knowledge on numerous points having express relation to them. Even since the last edition of my " Medical Notes," the rapid progress of Physiology — ever blending itself more closely with the general laws and inductions of physical science — has converted into certainty many things which could then be offered only as surmises, unsupported by any direct proof.

Much of course will be found in this volume which is familiar to those who have studied the subject, especially of late years. But, if I do not deceive myself, there are still certain facts not heretofore duly recognised or defined, and certain relations of phenomena requiring fuller illustration than they have yet received. These I have sought to embody in the ensuing Chapters, in the order which seems best calculated to give

THE FIRST EDITION. XI connexion and unity to the whole. To arrange under new combinations what is already known to uSj is often in itself a source of fresh knowledge, or a valuable means of correcting previous error. Various instances to this effect will, I trust, occur to the reader in his progress through the volume. I may add, that in the discussion of the subjects, though obliged to adopt certain divisions for the sake of clearness, I have kept in constant view that great law of continuity, which equally governs all mental and material phenomena. No conclusions are more secure, or more profitable, than those drawn from a careful notice of continuous relations ; and of those gradations of change, which bring extreme cases within common laws, and reconcile anomalies with facts familiar to experience. To this I would advert, as a principle I have largely applied in every part of the volume.

The topics treated of are such in their nature as perpetually to bring us to the very confines of metaphysical speculation. Except in the case of one great question, which could not be put aside, I have carefully avoided passing over this boundary. Convinced of the general truth of the

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maxim, that " it is safer and easier to proceed from ignorance to knowledge than from error," I have endeavoured throughout to separate what is known from that which is unknown — what is capable of being reached by the human understanding from that which is presumably unattainable by it. The close adherence to this principle will probably expose me to the charge of having surrounded the subject with unresolved doubts and difficulties. But I think it far better to incur this imputation, than to assume a knowledge not yet possessed, or to cover the deficiencies of reason by any mere artifices of language.

In different parts of this volume I have had occasion to advert to those Mesmeric phenomena and doctrines, and the topics collateral to them, which have draAvn so largely upon public attention of late years. Having the interests of truth solely in view, it has seemed to me that such reference might most legitimately, as well as most usefully, be made, through the relation of the phenomena in question to those other parts of physiology, which I believe to explain their real nature, and the conditions on which they

THE FIRST EDITION. Xlll

chiefly depend. To this principle I have adhered in every part of the discussion.

I prefaced my former work by a Chapter on the principles of Medical Evidence. I have retained this, with certain additions made to it, in the present volume ; since, though not directly associated with the subjects now treated of, the principles it suggests are of equal importance here, and cannot safely be neglected in any part of the discussion.

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