That the sensory activity of the soul has its centres in the cerebrum was
in SWEDENBORG’s time considered quite certain, but it was not so certain
as to just what part of the brain it was in which the soul’s activity
arose.
It is well known that the philosopher DESCARTES († 1650) had supposed
that the _glandula pinealis_ (pineal gland) was the seat of the soul, and
that the conscious perceptions came into being in this gland and in the
central ventricle of the brain, the ›_third ventricle_›, from which the
nerves, according to his opinion, took their origin.[59]
Gradually, however, there seems to have been more and more an inclination
to attribute this phase of the operation of the soul to _the white
medullary substance_ around the ventricles of the brain. And in
SWEDENBORG’s time this opinion seems to have been the usual one. At least
the matter is so presented by HERMANN BOERHAAVE, who, as is known, in a
high degree had the ear of his contemporaries.[60]
And even HALLER, some twenty years after SWEDENBORG had written his
works on the brain, was still of a similar opinion, as is evident from a
quotation which I shall here bring forward, in which he emphasizes that
neither perceptions nor the impulses to motion arise in the cortex of the
cerebrum, but in the medullary substance: ›Non ergo in cerebri cortice
sensus sedes erit, aut plena causae muscularis motus origo: eritque
utraque in medulla cerebri, & cerebelli.› (ALB. V. HALLER: ›Elementa
physiologiae›, Lausannae, 1762, Tom. IV., p. 392). But when even HALLER
would not attribute the soul’s activity to the cortex, what then can have
led SWEDENBORG to such a thought?
In order to clear up this question let us first examine the _anatomical
literature_ before SWEDENBORG’s time. And then we find that the
BARTHOLINS had already in a kind of way associated this branch of the
soul’s activity with the cerebral cortex, because they supposed that
the ›_spiritus animalis_›, (the ›spirits of life›), _was contained in
the cortex for the sensory functions_, just as it was conserved in the
medullary substance for the motor functions.[61]
And THOMAS WILLIS considered that the _›spiritus animalis› was generated
in the cerebral cortex_, but afterwards underwent proper elaboration and
distribution in the medulla of the cerebrum; and that the memory had its
seat in the cerebral cortex.[62]
And MALPIGHI (1628-1694) had expressed the surmise, that the minute
_cortical elements_, so particularly described by him, which correspond
to what we now call the nerve-cells of the cortex, were small glands,
›glandulæ›, whose function was to _prepare a substance which_, conveyed
through the nerves, _calls forth perceptions_.[63]
It had also been shown by the researches of MALPIGHI that these
›glandulæ› put forth a vessel-like fibre, which continued into the
cerebral medulla; and that this medulla for the greater part consisted of
such fibres or vessels.[64]
In how far these structures were ›fibres› or ›vessels›, and whether
they proceeded from (›oriuntur›) or terminated in (›desinunt›) the
small cortical elements, MALPIGHI leaves undecided. And when BOERHAAVE
afterwards in his lectures on the brain describes these structures, he
still depicts them as the finest tiny canals, which take up the ›spiritus
animalis›, pressed into them from the cortex, and transport it down to
the medulla oblongata, whence it is afterwards, by means of the nerves,
distributed to the different parts of the body. This ›spiritus› BOERHAAVE
describes as elaborated in the cortex, ›fabrica mirifica corticis
praeparatus›.[65]
These observations and surmises have evidently exercised a great
influence upon SWEDENBORG’s conception of the function of the cerebral
cortex; but they alone could impossibly have aided him in reaching the
enlightened standpoint at which he arrived. No, the most determining
and decisive factor for him in this question evidently was a great mass
of _clinical and pathological observations_ which he had collected and
synthesized, namely, symptoms of disturbances of consciousness and
sensibility, which had been exhibited by such patients, who, as was shown
by post mortem examination, had been injured in the cerebral cortex.
And I shall later refer to some of these cases in connection with the
consideration of the brain’s motor functions, because these patients
nearly always also exhibited motor disturbances.
But even here I may quote some of SWEDENBORG’s own words, which will show
what importance he attached to these testimonies: ›It is the cerebrum or
the cortical substance in which the soul disposes and unfolds its purest
and most simple organic forms of activity, and what the cerebrum is,
appears from a change of the faculties in some diseases, as in apoplexy,
epilepsy, paralysis, etc., likewise in many morbid states of the animal
mind in a cerebrum wounded by various accidents;› (›The Brain›, No. 86).
And in another place he says: ›If the cerebrum is either inflamed or
obstructed, or flaccid, or injured otherwise, the intellectual faculty is
unsettled; as in paralysis, melancholy, in cases of delirium, in atrophy,
apoplexy, in fevers, and other diseases; nay, the determination of the
will also is similarly affected. For each single cortical substance
contributes its share to this intellectory, that is, to this organ of the
understanding, etc.› (›The Brain›, No. 104, r).
All these observations concerning the consequences of injury to the
cerebral cortex—and the above-mentioned discoveries regarding the
structure of the cerebral substance and the hypotheses concerning the
relation of the cerebral cortex and cortical elements to the ›spiritus
animalis› and the perceptions,—these _clinical_ and _anatomical
experiences taken together_ seem to have led SWEDENBORG to the conviction
that the activity of the soul and not least that just now in question,
the sensory, had its seat in the cortex of the cerebrum.
He now enters into a detailed analysis of the course of the sensory
nerves as far as they are able to be demonstrated (›in ipsius oculi
luce›), and he thus follows the optic nerves to the optic thalami, and
thence their radiation towards the cerebral cortex, the olfactory nerves
to the corpora striata or the medulla of the centrum ovale and from
there out towards its cortical surroundings, the auditory nerves to
the medulla oblongata and thence up toward the cortex of the cerebrum,
(›versus supremum corticem›), and in the same manner he follows the
nerves of taste and touch. (See Œc. R. A. II., No. 192; and III., No.
66). He cannot now follow further the particular fibres through the
medulla all the way to the cortex, of whose importance for consciousness
and sensibility he became convinced through the clinical experiences,
but here he must _suppose_ a connection, and he says: ›these effects
(conscious perceptions) could never be produced ... unless in every
quarter there were _a mutual connection and perpetual communication of
the cortical substance with the medullary_, as regards the fibrils ...›,
(as well as a special arrangement of the cortical elements and special
qualifications in them, of which more will be said later).[66]
From all this it is clear, that it was probably through _a combination of
clinical and anatomical experiences_ that SWEDENBORG secured the premises
for his conclusions that the centre of the soul’s sensory activity is in
the cortex of the cerebrum.