Swedenborg brought forward still more cases, so incomplete, however, that it is not worth while to repeat them here. But he had at hand a very large number of cases, as he says: ›phalanges observationum idem testificantium› (Œc. R. A. No. 154), or, as he says in another place, so many that a bare enumeration of them would fill two whole pages (Œc. R. A. II., 154).
Swedenborg had made a specially careful study of a great many cases of apoplexy and hemiplegy, which naturally, in so far as they affected the cortex, gave him direct guidance in judging of its function. And he also understood very well how to judge at the same time with regard to the importance of bleedings in the soft membrane of the brain, the pia mater, on and between the convolutions of the brain, the ›gyri›, and the pressure that these exercise upon the cortex, and the results of prevented circulation in cases of apoplexy. For in all these cases, he says, the transmission of blood to the cortex is checked, and by this the cortex was disturbed in its function, and this was the cause of the loss of sensation and of the paralysis. (Œc. R. A., III., No. 411 and III., No. 413; see also ›The Brain›, No. 89).
But Swedenborg had also directed his attention to that method of investigation which, to the brain physiologists of the present day, is the best aid for the examination of the motor functions of the cerebral cortex, namely, experiments on animals. He quotes such experiments, in which incisions had been made into the cortex ›just to the marrow›, as it is expressed, (›usque ad substantiam medullarem› [Ridley], Œc. R. A., I., No. 505); or when the brain (in dogs) had been pierced, (Œc. R. A., II., No. 154), and how these injuries had occasioned spasms or contractions of the trunk or extremities (Ridley). He also describes such cases in which fine needles had been pierced through the dura mater and corrosive liquors introduced through the holes, with the result that severe disturbances occurred in both motility and sensibility, and also how through such injuries muscular contractions had been provoked, by which it was sometimes observed that with certain stimuli the contractions first occurred in certain groups of muscles (for example, in the head or neck) and afterwards spread to the other parts of the body. (Baglivi ›The Brain›, No. 20).
As will be seen, these experiments were no ›precision-investigations›; and the same may be said of the clinical and pathological ones. And this may be the more easily understood, when we consider that in those times so much interest was not attached to such special observations of pathological changes in the cerebral cortex; for this was then regarded only as a gland, a secreting organ or reservoir for the ›spiritus animalis›. These observations were therefore made more as it were in passing. The same is also true of the experimental investigations on animals, quoted above. These were in reality made not in order to investigate any function of the cortex, but for other purposes, namely, in order to search out the causes of the pulsations of the brain, or the qualities and functions of the dura mater, etc.
Yet, as we shall see later on, some of the cases, in the original descriptions, really contain statements somewhat more exact and of greater interest even for the theory of cortical localizations, than those which Swedenborg quoted; but he seems to have here adduced no more than what had reference to the cortex regarded as a whole, and which showed what great changes in both the power of sensation and motion injuries in the cortex could produce. If we take this into consideration, and if we synthesize all these experiences, and add to this the increased knowledge concerning the minute structure of the brain, which had been produced especially by Malpighi’s discoveries, we must admit that Swedenborg had good reasons for his view that the soul’s activity had its seat in the cortex of the cerebrum.
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).