Hughling Jackson's Researches on the Nervous System

Hughling Jackson's Researches on the Nervous System

Clinical and Physiological Researches on the Nervous System. (Reprints). No. 1.--On the Localisation of Movements in the Brain. By J. Hughlings Jackson, M.D., F.R.S., Churchill, 1875.

The author here reprints a paper (25 pp.), on the anatomical and physiological localisation of movements in the brain by study of paralysis and convulsion, which appeared in the Lancet in 1873; adding in an appendix two reports by Dr. Gowers, confirmatory of the views expressed in the paper, and in a somewhat elaborate preface (xlvii pp.), drawing out the general import of a series of investigations on the brain and nervous system which he has published from time to time in the last ten or eleven years. The reprint is extremely opportune both in itself and as giving occasion for this statement of the author's position in relation to the more recent experimental labours of Hitzig and Ferrier. The author is remarkable for the careful heed he has given throughout his inquiries to the latest results of psychological science, while he has at the same time a singularly clear apprehension of the limits of his functions as a clinical and physiological observer. No recent piece of work from the physiological side is more worthy of the attention of psychologists than this reprint with its weighty preface.(9 § 3 ¶ 1)

The fundamental position maintained by the author--a position which he has held from the beginning, but which, as far as regards expression, has become moe clearly defined in the course, of his researches--is that the physical substrata of mental states are sensori-motor processes, or, in other words, that the organ of mind is made up of processes representing impressions and movements. This amounts to saying that the higher and highest parts of the nervous system, known to be involved in conscious mental action (intellection, feeling, volition), are built on the same ground-plan as the lower parts with their function of simpler reflex action; and the author puts forward the view as the only one consistent with the doctrine of organic evolution. He prefers, for his own part, to call these sensori-motor processes the anatomical substrata of mind, but is careful to add that he thereby implies nothing as to the metaphysical relation of mind to the nervous system, the expression being reconcilable with very different opinions (some of which he cites) on that head. What he does seek most positively to convey is that in the brain there can never be question of aught but processes representative of impressions received primarily at the peripheral endings of afferent nerves, or representative of movements operated ultimately by efferent nerves through muscles; and that, in fact, the representation is always one conjoining both impressions and motor-impulses. Such being the fact, neither more or less, on the physical side at every stage of brain-development up to the highest in the convolutions, he strongly condemns the language of those physiologists who speak as if at some place in the higher parts of the nervous system we abruptly cease to have to do with impressions and movements, and begin all at once to have to do with mental states. He contends, in short, for thorough-going parallelism between sensori-motor brain-processes and conscious mental states, in the sense at once of correspondence and absolute distinctness, and no one has ever expressed the general relation more clearly and forcibly. The question of the downward limit of this relation between the physical and the psychical, he touches but leaves open.(9 § 3 ¶ 2)

From this position, then, he defends his special assumption that the study of paralysis and convulsion, leading to the localisation of movements and impressions in the brain, has a most important bearing on the physiological investigation of the substrata of mind. Before Hitzig and Ferrier began to practise direct stimulation of the exposed surface of the brain in animals, Dr. Hughlings Jackson had been led, by clinical observation of human patients, followed up by autopsy, to general views regarding the structural and functional relations of the different parts of the brain which their experiments but served to confirm. To their labours he does ample justice--indeed he speaks of them with the most generous enthusiasm--but he rightly urges that his own method of research must continue to be followed for the human brain. His main conclusions may be shortly given--(1) In disease of the brain (whether by destruction or over-discharge of parts--paralysis or convulsion), the most voluntary or special movements, faculties, &c., suffer first and most; this he calls a principle of Dissolution, reversing the order of Evolution. (2) The convolutions near the corpus striatum re-represent the movement represented in that centre. (3) The same muscles are represented in different order in several places; although, therefore, muscles may be convulsed by discharge from a particular part of the brain, they need not by paralysed by its destruction. (4) The movements of the two sides of the body are represented in each half of the brain. (5) The two halves of the brain are not duplicates: there is a leading side--the left in most people--for voluntary movements, the right side serving for corresponding automatic movements. (6) The anterior is the chiefly motor, and the posterior the chiefly sensory, region of the cerebrum; their distance apart and multiplicity of connections having a meaning in relation to the power we have of forming new combinations out of the elements of mental experience. (7) All the movements of the body, while represented in the cerebrum, are represented also, but in a different order in the cerebellum. The reader is referred to the reprint and the preface for the evidence upon which these conclusions are founded. Before closing this short notice, I wish, however, to draw attention more particularly to the discussion extending from p. xx. to p. xxxvii., where the author in proof of his main thesis that sensori-motor processes are the physical substrata of mental states, takes words and visual forms as examples, and shows that, whether the mental experience is representative or presentative, the brain-process is equally sensori-motor, involving both seats for receiving impressions and the centres whence motor impulse proceeds. The whole argument is excellently conducted, and displays rare psychological acuteness. Should it be said that the instances are not quite decisive of the general position, being cases in which the presentative experience--actual speaking and seeing--too manifestly involves direct muscular activity, the author might reply that it was important to choose examples about which there could be no mistake; but, in fact, the case of vision is one which it needs no small amount of psychological training to apprehend rightly. Physiological observers, even when they duly appreciate the import of the motor element in speech, often fail to understand its import in the explanation of objective knowledge generally. It would not be easy to urge the latter point more effectively than it is done here by Dr. Hughlings Jackson.[32](9 § 3 ¶ 3)


9 § 3 n. 1. Since the above notice was written I have seen a series of three papers on Psychology and the Nervous System contributed to the British Medical Journal in September and October last. The writer, who is evidently Dr. H. Jackson himself, while expounding the main positions of the pamphlet here noticed, supports them with new and important evidence. One paragraph bearing on the question last touched of the part played by muscularity in vision, contains an argument so neatly put and so decisive that it deserves to be quoted in full:--

There are many morbid conditions which show the importance of muscularity, or of action of nervous centres representing movements, in the estimation of the extension of objects. By altering movements of our eyes, we alter the size of objects, if this expression be permitted. For example, if we impress the retina with a flame, and thus obtain an after-image, we find that this varies greatly in size as we look near or into the distance. Yet the sensory element concerned--the retinal area affected--is unaltered during the differences of ocular adjustment. There is even more than this. By different adjustments of our eyes--that is by altering the motor element--we may to some extent alter not only the size, but the shape, of these spectral images. Thus, if we impress the retina by a circle, and then project the after-image on to an inclined sheet of paper, our spectral circle becomes oval; a spectral square becomes oblong. This is a very remarkable illustration, showing the importance of movement in the estimation of shape. In both cases, the retinal (sensory) element is unaltered. The differences in size and shape are owing to differences solely in the motor element.--British Medical Journal, Oct. 2nd, 1875.

The writer also draws attention to Dr. Weir Mitchell's remarkable work on Injuries of the Nerves, which furnishes evidence strongly confirmatory of the doctrine that the so-called muscular sense accompanies the out-going of motor-impulse by the efferent tracks--a doctrine associated in this country with the name of Professor Bain, and in Germany chiefly with the name of Professor Wundt.