BOOK I. § 51. The nerve movements. be lost, and the fact once stored up in memory stored up now no longer. But, in speaking of nerve movements as the cause of conscious states, it must not be forgotten that every such movement takes place only at the expense of some waste of the living nervous substance, and that this waste is repaired by a new growth in which the habit of movement in the old way is strengthened, so that the oftener a movement has been repeated the more easily is it repeated again. Every movement which has once taken place becomes thus represented by a perhaps very minute change in the structure of the nervous substance, which grows with exercise; and every movement may thus, conceivably at least, be capable of reawakening on the occurrence of an appropriate stimulus. (See Dr. Maudsley's Phys. and Path. of the Mind, p. 67.) Yet since this circumstance is common to all cases of nerve movement, and presumably affects all alike, I shall make no further mention of it in speaking of the nerve movements as causes of states of consciousness. 2. Obvious as this conception of two kinds of movements, the one belonging to the nerve itself, the other to the stimulus, may perhaps appear, it is far from depending solely on a priori grounds. If we admit the doctrine of Prof. Du Bois Reymond, which is the foundation of the greater part of the results obtained by modern investigation of nervous action, that the electric current in living nerve is a constant property of it, varying with its power of performing its normal functions, we have in that current the means of testing the presence of the former kind of movements by themselves, and of measuring their degree of vigour. In that case, the movements pro per to the nerve substance itself are no longer an hypothesis but a fact, and one concerning which, it may be added, no inconsiderable knowledge has been already acquired. We must then distinguish three states through which the nerve substance passes in the performance of its functions; the first, when it is the seat solely of the movements of action and reaction between its own particles, in which, since it is not engaged in producing either perception or muscular motion, it is said to be in a state of rest but stimulable, ruhend, erregbar; the second, when some stimulus, either from within or from without, combines with this state, so as to intensify its movements, which we may call the state of tension, erhöhte Erregbarkeit; and the third, when an additional or prolonged stimulus is combined with the movements of the state of tension, so as to set on foot those movements upon which follows actual perception or muscular motion, which may be called the state of activity of the nerve, its Erregungszustand. And each of these states can be examined separately, and its phenomena subjected to various electrical tests. Funke's Lehrbuch, 2nd Book, 1st Abschnitt, and more particularly § 139, 142; 146, 150; 155, 157. These enquiries however are not to our present purpose, which requires rather that we should apply the foregoing analysis of nerve movements to the corresponding phenomena in states of consciousness. 3. The chief application perhaps of this analysis is to explain the different degrees of vigour in perception and muscular action of different persons. The result of the state of activity of the nerve is perception or muscular action, and this result must vary in character according to the parts played respectively Воок І. CH. III. $51. The nerve movements. Book I. $51. The nerve movements. by the two contributors to that activity, the movements of the nerve itself and those of the stimulus. A nerve whose own movements of action and reaction are vigorous and elastic will not only, under the same stimulus, produce more vivid perceptions and stronger muscular motions than one less vigorous and elastic, but will react more forcibly upon the movements of the stimulus itself, so as to be less permanently affected by them. A weaker nerve will have less power of reacting upon the movements of the stimulus. The perceptions of the former, and the specific sensations of pain and pleasure which accompany them, will be more vivid, but also will be less important as bearing a less proportion to its total powers. Those of the latter will be less vivid, but it will have that general mode of pain more constant which consists in the feebleness of reaction; while the vigorous reaction of the former will be an additional and general mode of pleasure. In the vigour of reaction between the nerve's own movements and those of the stimulus lie the different degrees of pleasure or of pain which are general, or common to all states of consciousness alike; while the specific feelings of every kind, including their specific pleasures and pains, depend upon the vigour of these two movements added together. The weaker nerve will then receive less intense specific feelings than the stronger, from the same stimulus, and at the same time will be more exposed to general feelings of pain, less open to general feelings of pleasure, which depend on the degree of reactive vigour. By breaking up the combined movements of the active state of nerve into movements derived from the nerve itself and movements derived from the stimulus, we not only explain why persons of feeble sensibility appear to suffer from their feelings so much more than those whose sensibilities show signs of being more acute, but we also obtain a physiological foundation for the distinction between general and specific pleasures, a distinction which, with its physiological foundation, the distinction between two separate kinds of nerve movements, will be found of importance in all departments of the present enquiry. § 52. 1. The presentative perceptions of sense have been sufficiently described in Chapter ii. Part i.; let us turn now to the organs appropriated to them, not however to describe minutely their structure or functions as organs of sense, but in order to distinguish them from the organs appropriated to the functions which, in metaphysical analysis, follow next in order upon presentative perceptions, by combining them into and with representations more or less complex. The peripheral extremity of every nerve of sense is like a hand stretched out by the central organ to grasp the peculiar impression which it receives from the world without, or from the part of the body to which it goes. It is requisite that its connection with its central organ should be kept up; and its peculiar effect, the impression received and imparted by it, is due to the changes which are wrought by stimuli in its peripheral apparatus acting upon the nerve in its entire length, including the cell or cells which are its central termination. 2. Apart from the nerves belonging to the sympathetic system, which need not I think be brought into our enquiry, all the nerves of sense and motion have the cells which form their central terminations embedded in portions of the nervous organism which VOL. I. AA lie below the cerebrum and cerebellum; that is to say, in the spinal cord, the medulla oblongata and parts immediately adjacent, the grey matter which forms the floor of the 4th ventricle, the optic thalami, and corpora striata. Of these nerves, the greater part of the nerves of touch and muscular motion, being distributed over the body, terminate in the spinal cord, while those of them which supply the head and face terminate in or above the medulla oblongata, in the same regions where the other nerves of special sense terminate. One exception to this statement may perhaps be found in the nerve of the first pair, the nerve of smell. If this is a nerve, it would be an important exception, since two of its three roots have been traced into the cerebral hemispheres. Mr. G. H. Lewes argues that it is not a nerve; Phys. of Common Life, Chap. x. But supposing it to be the nerve of smell, it would not invalidate the view here taken, since it has one root which enters into the same nervous mass with the rest, while its additional and peculiar connection with the cerebrum might perhaps furnish an explanation of the peculiar action of odours upon the memory, summoning up in an instant long past scenes with a vividness and a rapidity which belong to the perceptions of no other sense. 3. With the above exception, then, it may be said that the spinal cord and the mesocephalic group of organs, the highest members of which are the corpora striata and optic thalami, form a mass which is distinguished from the cerebrum and cerebellum by its containing the central terminations of all nerves of sense and muscular motion. The whole nervous organism falls thus into three divisions; 1st, the nerves from periphery to central termination; 2nd, |