THE DOCTRINE OF LOCALIZATIONS.
But Swedenborg, as is well known, did not stop here. The cerebral cortex certainly constituted a whole which transformed the sensations into thoughts and determinations, but all the regions of the cortex were not of the same degree: some ruled the higher, others the lower functions, thus also containing subdivisions, in some of which the sense-impressions were received, in others from which the motor impulses proceeded. (See ›The Brain›, Nos. 66, 68, 71, 88, 98, 100, 102, etc.).
This conception of the brain appears at first glance as very modern. But upon searching the literature before Swedenborg’s time one finds that the thought was not so entirely original. New was the thought of attributing the psychical functions to the cortex, new also was the attempt to accurately determine upon the place where the different functions originate; but the idea of localization itself is found again in the literature which Swedenborg already had at his disposal.
Boerhaave, for instance, says, in his ›Institutiones medicæ›, when speaking of the sensations, that they give rise to different perceptions, partly owing to the differing species and nature of the outer objects, and partly to the different natures of the sense-organ and the affected nerve, but partly also to the different regions in the cerebral medulla from which the nerve proceeds. Thus we have here a kind of localization to a special region of the brain, although in its medulla.[71] And still more clearly does Boerhaave express the same idea in his ›Prælectiones academicae,› where he says: ›In the ’Sensorium commune’ there are regions locally distinguished for the different senses, just as every sense has its own special sense-organ.›[72]
And before Boerhaave the philosopher Descartes had expressed an idea concerning a certain form of localization of the various elements of psychic activity. For he supposed that the images of sensation and the images of the memory, etc., which the soul perceives, arise on those places on the walls of the brain’s central ventricle, where, according to his opinion, the various nerves originate. In a similar way he also imagined the origin of motility localized. (R. Descartes: ›De homine›, publ. by F. Schuyl, Ludg. Bat., 1662).
We here reproduce some illustrations from the work of Descartes just mentioned, which are designed to show how he thought that the images of sensation arise. — — See the figures 1, 2, 3.
We thus see that the idea of localization itself was not altogether new. But how did Swedenborg ultimate and develope it?
With regard to function Swedenborg divided the hemispheres of the cerebrum into two parts: one anterior region and one posterior, conceiving the fissure of Sylvius as the dividing boundary between them. (›The Brain›, Nos. 16, 88, 91).
Transcriber’s Note: Click for larger version.
Fig. 1. Fig. 2. Fig. 3. Fig. 4.
Figures 1-3. Reproduced from Descartes: ›Tractatus de homine›.
Fig. 1. A part of the wall of the central ventricle of the brain. The points of the dotted area represent the openings of the nerves, which, according to the opinion of Descartes, take their origin in the wall of the ventricle. The figures O (star) and B (lily) are formed by combinations of such nerve openings.
Fig. 2. View of the left hemisphere from the medial side. The dotted area B represents the place, where, according to Descartes, the nerves originate. The vesicle H is the pineal gland, wherein the soul was thought to have its seat.
Fig. 3. Illustrates the act of seeing. The object ABCD forms an image, 1357, on the retina of the eye. This image provokes a similar image, 2468, on the wall of the brain’s ventricle, by exciting a stream of ›spiritus animalis› from the central ventricle through certain of the fine nerve tubules of the optic nerve, the openings of the nerve tubules in the wall of the ventricle being widened and thus forming images (of sight), which the soul is able to perceive from its seat in the pineal gland.
Fig. 4. Reproduced from Vieussens: ›Neurographia universalis›, Tabula XVI. Illustrates the passage of the coarse fibres of the middle region of the brain’s medullary substance through the capsula interna, pons and the pyramids on the front of the medulla oblongata downwards to the anterior part of the spinal cord.
To the anterior region he attributed the actual operation of the soul, while he supposed that the posterior region was chiefly engaged in the animation of the blood. He adds, however, ›it cannot be denied that sensations reach even the posterior region of the brain, yet our mind does not become conscious of them to the same degree as it does in the anterior region› (›The Brain›, No. 71).
In this anterior region of the cerebrum he distinguished three lobes, or so called ›curiae›, the first one highest up, ›in the crown›, a middle one below it, and a third one lowest down, i. e., nearest to the fissure of Sylvius.[73] In these three lobes the actual psychic life is developed, and that so much the more clearly and perfectly, the higher up in the region these intricate processes occur. It is here that perceptions, thoughts, judgments, conclusions, come into being; it is from here that ultimately will and determination issue. (See ›The Brain›, Nos. 12, 66, 71, 88, 98, 100, 102).
As regards the sensory part of the psychic activity, Swedenborg does not make any attempt at a detailed localization; but as regards the motor functions he arranges their centres within the above-mentioned regions as follows: ›The muscles and actions which are in the ultimates of the body or in the soles of the feet seem to depend more immediately upon the highest parts (of the brain), upon the middle lobe the muscles which belong to the abdomen and thorax, and upon the third lobe those which belong to the face and head;› and he adds, ›for they seem to correspond to one another in an inverse ratio› (›The Brain›, No. 68).
Whence did Swedenborg get all this? Whence the whole of this doctrine of localizations? In his first great anatomical work, ›Œconomia Regni Animalis›, nothing is said about it; first in his last anatomical work, ›De Cerebro›, is it advanced, and then — — — quite finished! One is at first glance tempted to think that he had succeeded in finding some new clinical experiences, upon which he could found this doctrine. For he had not even finished the account of the function of the brain’s anterior region, before interjecting: ›Therefore, if this portion (the anterior region) of the cerebrum is wounded, then the internal senses—imagination, memory, thought—suffer; the very will is weakened, and the power of its determination blunted. This is not the case if the injury is in the back part of the cerebrum› (›The Brain›, No. 88). But afterwards he does not bring forward (in ›De Cerebro›) any observations which could serve as proof with regard to this. And if one examines the cases he has referred to in his preceding works, one cannot possibly arrive at the localization of the psychic functions which he has here (in ›De Cerebro›) sketched; for the evidence concerning the position of the injuries in the cortex are entirely too scanty and incomplete. But if we consult the original descriptions, we find there many other and more particular data than those quoted by Swedenborg when he was only concerned in explaining the function of the cortex as a whole. Wepfer, for instance, reports in his ›Historiæ apoplecticorum› concerning the woman seventy years of age, who suddenly lost the power of speech, that the cavity, filled with blood, which was found in the cortex at the autopsy, was located in the right hemisphere, just behind the forehead (›ad frontem fere antrorsum›), and that it extended rather far both backwards and upwards; even measurements were given (length 8, breadth 4, depth about 2 uncias). It was also stated that the blood-vessels whose bursting caused bleeding belonged to the antero-lateral branches of the carotid artery in the brain. It is also mentioned that no changes were found in the left hemisphere of the brain; and from the clinical account it appears that even after the stroke the woman was able to move the extremities of the right side.[74] — — — All this indicates quite evidently that the lesion of the cortex was situated in the anterior region of the brain!
And Pacchioni reports concerning the youth, who was afflicted with the right-sided facial paralysis, that even the extremities of the right side were somewhat paralysed, and that the cyst, which at the post mortem examination was found on the left hemisphere, extended from the crown to the region of the temple (›a capitis vertice in temporalem regionem›).[75] Thus this case also furnishes an unmistakable indication that the cortical lesion was situated in the anterior region of the brain.
It seems strange that Swedenborg did not here supply an account of these interesting and convincing cases, which he nevertheless, as we have seen, was well acquainted with. For his habit is to furnish the chapters of his works with an introduction in which he reports, often in very detailed form, the statements of the authors upon which he bases his conclusions. Since in the present case such an account is lacking, this may depend: either upon the fact that this last anatomical work of Swedenborg, ›De Cerebro›, was not quite completed and finally edited for the press, or thereon that Dr. Rudolf Tafel, who edited the translation which is now accessible in print, excluded it. For Dr. Tafel says in a note that the introduction to the chapter in question would be introduced into Part II., chapters 1 and 2, but—Part II. was never printed! Since, however, the Royal Swedish Academy of Sciences will publish ›De Cerebro› in its edition of Swedenborg’s Scientific works, this question will no doubt be cleared up. But this much is quite clear from what has already been adduced, that the cases of paralysis which Swedenborg previously quoted in a brief form are in the original descriptions reported so completely and in such detail that one can without the least doubt localize the cortical lesions reported in those cases in the anterior (superior) region of the cerebrum.
We now pass to an examination of the anatomical literature to which Swedenborg had access. And, as we shall find, we can here see whence Swedenborg derived material for his detailed doctrine concerning the function of the brain’s anterior region. This becomes evident on comparing Swedenborg’s mode of thinking of the brain’s psychical activity with the descriptions of preceding authors in anatomy.
The group of nuclei, ›corpus striatum›, in the cerebrum had been an object of special interest for preceding authors.
The Englishman, Thomas Willis, had for example in his ›Cerebri anatome› (published in 1667) portrayed them as a kind of junction, ›internodes›, by which the cerebrum coheres with the medulla oblongata; and he pays special attention to it on account of its peculiar structure (›The Brain›, No. 476); and he is said even to have attributed to them the ›Sens commun›.[76]
And the professor in Montpellier, Raimond Vieussens, had given in his ›Neurographia universalis› (published in 1685) a very exact description of the ›corpus striatum›, (not only of its ›superior nuclei›: ›Corp. striat. sup. ant.› = Nucleus caudatus and ›Corp. striat. sup. post.› = ›Thalamus opticus›, but also of its lower lateral nucleus = ›Nucleus lentiformis›) as also of the mighty medullary tract of nerve fibres, i. e., ›capsula interna›, which passes through the same, and which on the one hand is distributed to the brain, especially to its anterior (superior) region, and on the other hand by means of the nerves radiates into the various parts of the body.
(In order to facilitate orientation we may refer to C. Toldt: ›Anatomischer Atlas›, 1899, 8 Lieferung, Fig. 92: ›Querschnitt des verlängerten Markes und der Gehirnstiele. Verlauf der Pyramidenbahn von der Pyramidenkreuzung an durch die Pyramide, die Brücke und die Basis des Grosshirnstiels in die innere Kapsel, woselbst sie in den Stiel des Stabkranzes, Pedunculus coronæ radiatæ, eingeht.›)
Swedenborg, who had studied and often quoted both Willis and Vieussens, likewise attributed a very great significance to the corpus striatum. All the sensory impressions pass through it to the brain, and all the voluntary impulses to motion pass out by the same path. (›The Brain›, No. 67). ›It is›, says he in his figurative way, ›in a certain sense, the Mercury of the Olympus; it announces to the soul what is happening to the body, and it bears the mandates of the soul to the body› (›The Brain›, No. 67).
And as the corpus striatum lay most immediately under the anterior (superior) region of the brain, and was in close connection with it, so the sensory impressions would for the most part pass to this region, and the voluntary impulses to motion would likewise proceed from it (›The Brain›, Nos. 66, 67).
The same Vieussens had furnished a very detailed description of the passage of the nerve tracts in question, which pass through the corpus striatum and capsula interna, and had followed them both upwards towards the hemispheres of the brain and downwards towards the spinal cord. When he followed them upwards, he found that they formed three regions in the ›centrum ovale›: the regio superna, highest up nearest the crown, the regio media, in the middle, and the regio infima, lowest down, and consequently nearest the fissure of Sylvius. (R. Vieussens: ›Neurographia univ.›, pp. 115 and 117).
In these regions of the cerebral medulla, especially in the highest, Vieussens considered that the soul’s activity had its seat: with the help of ›spiritus animalis› the soul here had an opportunity of receiving the sensory impressions, and in the fine and finest nerve fibres there were here formed sensory images, conceptions, (Op. cit. p. 129), here the memory images were preserved, (Op. cit. p. 135), and here the faculty of judgment had its seat, (Op. cit. p. 137), etc.
In these regions, especially in the highest, the will also had its seat and origin, and at its command the ›spiritus animalis› streamed out through the nerves, thus conveying the impulses to motion to the various muscles of the body. (Op. cit. pp. 122, 123, 188, et seqq.).
For Swedenborg, who had arrived at certainty with regard to the seat of the soul’s activity in the cerebral cortex, and not in the cerebral medulla!, and who through Malpighi and others had been led to see that the fibres of the cerebral medulla were continuations of the processes of the cortical elements,—for Swedenborg it naturally lay very near at hand to follow the fibres of the three regions of Vieussens out to the cortical substance on the surface of the brain; and so Swedenborg has his three cortical lobes! And to them, especially to the highest, he could now attribute the source of the soul’s life.
When Vieussens followed the nerve tracts of the corpora striata and capsula interna downwards, he found:
that the fibres of the uppermost region led down to the posterior region of the spinal cord; (›ad posticam spinalis medullæ regionem›);[77]
that the fibres of the middle region, which were especially coarse and traversed the capsula interna and pons, forming thick tracts, could be clearly followed down into the anterior portion of the spinal cord, (›in anticam spinalis medullæ partem›), where they came into connection with the anterior origins of the spinal nerves, (›ad antica nervorum spinalium principia›), also paying, on their passing through the medulla oblongata, ›necessary tribute›, (›necessarium vectigal›), as it is expressed, to certain of its nerves;[78]——See the figure 4!——
that the fibres of the lowest region were distributed to certain nerves, which proceed from the medulla oblongata, and to some of the anterior origins of the spinal nerves (›quædam illius pars ad quosdam e Medulla oblongata prodeuntes, altera vero ad antica nervorum spinalium principia›).[79]
In Swedenborg’s time it was, however, known that the muscles which produce the movements of the head and face receive their nerves just from the medulla oblongata and the uppermost part of the spinal cord; and it therefore lay near at hand for Swedenborg, when he saw that paralyses arose when certain cortical regions were destroyed, to draw the conclusion, that the muscles and movements which belong to the face and head, depend more immediately upon the lowest region of the third lobe of the cerebral cortex.
And as it was also known that the muscles of the thorax and abdomen receive their nerves from the superior portion of the spinal cord, whither just the tracts of coarse fibres from the middle region of the brain could be followed, (see figure 4), so Swedenborg could likewise draw the conclusion from this that the muscles and movements which belong to the thorax and abdomen depend more immediately upon the middle region or lobe.
It might now appear tempting to continue the conclusion by connecting the remaining highest lobe and the lower extremity. But probably Swedenborg did not consider that he had sufficient ground for this. The description by Vieussens did not here furnish any suitable guidance, for it was possible that the coarse fibres of the middle region continued so far down into the spinal cord that they could innervate not only the muscles of the abdomen but also those of the lower extremity. For this reason Swedenborg refrains from localizing exactly the centre of motion of the lower extremity and contents himself with stating in general terms only that this centre might lie above that of the abdomen. He therefore says: ›the order seems to be so disposed that——the muscles and actions, which are in the ultimates of the body, or in the soles of the feet, depend more immediately upon the highest parts (of the brain)›, whereas concerning the thorax and abdomen he says that they depend upon the middle lobe, and of the head that it depends upon the third lobe. (›The Brain›, No. 68). I believe that this is the reason why Swedenborg’s doctrine of localizations as concerns the motor centre of the lower extremity is expressed in such vague terms.
From a comparison of these descriptions by Swedenborg and Vieussens we have found that there are such considerable similarities between them that they in many respects agree point for point. And it therefore seems to me rather probable that Swedenborg derived his conception of the more detailed localization of the soul’s activity from the descriptions of Vieussens.