in a scientific spirit, the laws of its functions, and to trace the resemblances which undoubtedly exist between them and the functions of lower nerve-centres.

Take, for example, the so-called faculty of memory, of which metaphysicians have made so much as affording us the knowledge of personal identity. From the way in which they usually treat of it, one would suppose that memory was peculiar to mind, and far beyond the reach of physical explanation. But a little reflection will prove that it is nothing of the kind. The acquired functions of the spinal cord, and of the sensory ganglia, obviously imply the existence of memory, which is indispensable to their formation and exercise. How else could these centres be educated? The impressions made upon them, and the answering movements, both leave their traces behind them, which are capable of being revived on the occasions of similar impressions. A ganglionic centre, whether of mind, sensation, or movement, which was without memory, would be an idiotic centre, incapable of being taught its functions. In every nerve-cell there is memory, and not only so, but there is memory in every organic element of the body. The virus of small-pox or of syphilis makes its mark on the constitution for the rest of life. We may forget it, but it will not forget us, though, like the memory of an old man, it may fade and become faint with advancing age. The manner in which the scar of a cut in a child's finger is perpetuated, and grows as the body grows, evinces, as Mr. Paget has pointed out, that the organic element of the part remembers the change which it has suffered. Memory is the organic registration of the effects of impressions, the organization of experience, and to recollect is to revive this experience-to call the organized residua into functional activity.

The fact that memory is accompanied by consciousness in the supreme centres does not alter the fundamental nature of the organic processes that are the condition of it. The more sure and perfect, indeed, memory becomes, the more uncon

scious it becomes; and, when an idea or mental state has been completely organized, it is revived without consciousness, and takes its part automatically in our mental operations, just as an habitual movement does in our bodily activity. We perceive in operation here the same law of organization of conscious acquisitions as unconscious power, which we observed in the functions of the lower nerve-centres. A child, while learning to speak or read, has to remember the meaning of each word, must tediously exercise its memory; but which of us finds it necessary to remember the meanings of the common words which we are daily using, as we must do those of a foreign language with which we are not very familiar? We do remember them, of course, but it is by an unconscious memory. In like manner, a pupil, learning to play the piano-forte, is obliged to call to mind each note: but the skilful player goes through no such process of conscious remembrance; his ideas, like his movements, are automatic, and both so rapid as to surpass the rapidity of succession of conscious ideas and movements. To my mind, there are incontrovertible reasons to conclude that the organic conditions of memory are the same in the supreme centres of thought as they are in the lower centres of sensation and of reflex action. Accordingly, in a brain that is not disorganized by injury or disease, the organic registrations are never actually forgotten, but endure while life lasts; no wave of oblivion can efface their characters. Consciousness, it is true, may be impotent to recall them; but a fever, a blow on the head, a poison in the blood, a dream, the agony of drowning, the hour of death, rending the veil between our present consciousness and these inscriptions, will sometimes call vividly back, in a momentary flash, and call back too with all the feelings of the original experience, much that seemed to have vanished from the mind forever. In the deepest and most secret recesses of mind, there is nothing hidden from the individual self, or from others, which may not be thus some time accidentally revealed; so that it might well be

that, as De Quincey surmised, the opening of the book at the day of judgment shall be the unfolding of the everlasting scroll of memory.*

As it is with memory so is it with volition, which is a physiological function of the supreme centres, and which, like memory, becomes more unconscious and automatic the more completely it is organized by repeated practice. It is not man's function in life to think and feel only; his inner life he must express or utter in action of some kind-in word or deed. Receiving the impressions from Nature, of which he is a part, he reacts upon Nature intelligently, modifying it in a variety of ways; thus Nature passes through human nature to a higher evolution. As the spinal cord reacts to its impressions in excito-motor action, and as the sensory centres react to their impressions in sensori-motor action, so, after the complex interworking and combination of ideas in the hemispherical ganglia, there is, in like manner, a reaction or desire of determination of energy outward, in accordance with the fundamental property of organic structure to seek what is beneficial and shun what is hurtful to it. It is this property of tissue that gives the impulse which, when guided by intelligence, we call volition, and it is the abstraction from the particular volitions which metaphysicians personify as the will, and regard as their determining agent. Physiologically, we cannot choose but reject the will; volition we know, and will we know, but the will, apart from particular acts of volition or will, we cannot know. To interpose such a metaphysical entity between reflection and action thereupon would bring us logically to the necessity of interposing a similar entity between the stimulus to the spinal cord and its reaction. Thus, instead of unravelling the complex by help of the more simple, we should obscure the simple by

* An apt illustration, most true to Nature, of the recurrence of early Impressions in the delirium of dying, is afforded by Falstaff, who, as he expires in a London tavern after a life of debauchery, babbles of green ields.

speculations concerning the complex. As physiologists, we have to deal with volition as a function of the supreme centres, following reflection, varying in quantity and quality as its cause varies, strengthened by education and exercise, enfeebled by disuse, decaying with decay of structure, and always needing for its outward expression the educated agency of the subordinate motor centres. We have to deal with will, not as a single undecomposable faculty unaffected by bodily conditions, but as a result of organic changes in the supreme centres, affected as certainly and seriously by disorder of them as our motor faculties are by disorder of their centres. Loss of power of will is one of the earliest and most characteristic symptoms of mental derangement; and whatever may have been thought in times past, we know well now that the loss is not the work of some unclean spirit that has laid its hands upon the will, but the direct effect of physical disease.

But I must pass on now to other matters, without stopping to unfold at length the resemblances between the properties of the supreme centres and those of the lower nervecentres. We see that the supreme centres are educated, as the other centres are, and the better they are educated the better do they perform their functions of thinking and willing. The development of mind is a gradual process of organization in them. Ideas, as they are successively acquired through the gateways of the senses, are blended and combined and grouped in a complexity that defies analysis, the organic combinations being the physiological conditions of our highest mental operations-reflection, reasoning, and judgment. Two leading ideas we ought to grasp and hold fast: first, that the complex and more recondite phenomena of mind are formed out of the more simple and elementary by progressive spe cialization and integration; and, secondly, that the laws by means of which this formation takes place are not laws of association merely, but laws of organic combination and evo lution. The growth of mental power means an actual addi

tion of structure to the intimate constitution of the centres of mind—a mental organization in them; and mental derangement means disorder of them, primary or secondary, functional or organic.

Although I have declared the hemispherical ganglia to be preeminently the mind-centres, and although it is in disorder of their functions-in disordered intelligence, in disordered emotion, and in disordered will-that insanity essentially consists, it is nevertheless impossible to limit the study of our mental operations to the study of them. They receive impressions from every part of the body, and, there is reason to believe, exert an influence on every element of it: there is not an organic motion, sensible or insensible, which does not, consciously or unconsciously, affect them, and which they in turn do not consciously or unconsciously affect. So intimate and essential is the sympathy between all the organic functions, of which mind is the crown and consummation, that we may justly say of it, that it sums up and comprehends the bodily life that every thing which is displayed outwardly is contained secretly in the innermost. We cannot truly understand mind-functions without embracing in our inquiry all the bodily functions and, I might perhaps without exaggeration say, all the bodily features.

I have already shown this in respect of motor functions, by exhibiting how entirely dependent for its expression will is upon the organized mechanism of the motor centres-how, in effecting voluntary movements, it presupposes the appropriate education of the motor centres. Few persons, perhaps, consider what a wonderful art speech is, or even remember that it is an art which we acquire. But it actually costs us a great deal of pains to learn to speak; all the language which an infant has is a cry; and it is only because we begin to learn to talk when we are very young, and are constantly practising, that we forget how specially we have had to educate our motor centres of speech. Here, however, we come to another pregnant consideration: the acquired faculty of the