L'Aqueduc de Sylvius - rôle et fonctionnement in a LIVING BRAIN

 [ Note de A.C.: sur ce sujet précis et très complexe - qui fait appel à des connaissances infinies sur l'anatomie et la physiologie du cerveau - je fais ici le choix de privilégier les notes de l'éditeur, parce qu'elles me semblent sélectionner et synthétiser à merveille l'essentiel de ce que nous explique Sir Emanuel Swedenborg sur l'anatomie et le rôle de l'Aqueduc de Sylvius & de la Valve de Vieussens, au travers de l'ensemble de son Oeuvre Médico-Scientifique sur le cerveau. ]

The Brain, volume II, editor's notes, note VII, pp. 545 et ss., extraits: 

b. RELATION OF THE CEREBRAL AND CEREBELLAR LIQUIDS.

“3.  In our note iii. (Vol. I, pp. 713-718) we have shown fully, that in the living body the valve of Vieussens presents an effective barrier against the promiscuous mixing up of the cerebral and cerebellar liquids; that is, of the the liquids which are collected respectively in the cerebral or lateral ventricles, and in the cerebellar or fourth ventricle. In confirming this fundamental position of Swedenborg's theory respecting the liquids of the brain, we based ourselves on facts drawn from anatomy, pathology, amd chemistry. The fact drawn from chemistry seems to be conclusive in itself, for it is an acknowledged fact in the text-books of Organical Chemistry, that there is a radical difference in the chemical composition of the ventricular, that is, the cerebral fluid, and the cerebro-spinal fluid, that is, the cerebellar liquid (see Vol. I, pp. 726-727). This difference in the chemical composition of the two liquids arises from a difference in their function; for while the cerebrum, according to Swedenborg, through the ventricular liquid, “cares for the mass of the blood“, the cerebellum, through its liquid, “provides for the sujacent roots of the nerves.“ Yet in spite of this radial difference between the two kinds of liquids, which, according to Swedenborg, amounts to this, that the cerebral liquid is of grosser kind than that which is collected in the fourth ventricle (see no. 713), these liquids nevertheless seem to communicate under certain conditions - not in ths sense, however, that the cerebral liquid is instilled into the cerebellar (for the grosser should not be mixed with the finer), but that the cerebellar, that is, the cerebri-spinal liquid, under certain contingencies, is added to  the cerebral or ventricular liquid. This seems to be the reason why the valve of Vieussens does not interrupt entirely the line of communication between the fourth ventricule and the Sylvian aqueduct, that is, why it serves the purposes of a valve, and does not present itself anatomically as a membrane completely closing up said passage."

“The  contingencies. however, under which the valve grants a passage to the cerebellar liquid, seem to be these: Under ordinary circumstances, that is, so long as the contents of the third and fourth ventricles are evenly balanced, the communication between the two  is intercepted by the valves od Vieussens; but, when for any reason whatsoever the moisture in the lateral, that is, respectively in the third ventricle, is abnormally scanty, then the valve of Vieussens, under instructions received from the cerebellum, which superintends all the involuntary or vegetative processes in the human body, opens its flood-gates, and admits so much of the cerebellar wave, that is, of the cerebro-spinal liquid, as is required for the restoration of the equilibrium in the cerebral ventricles.“

“[...] . It is possible also, that the contents of the fourth ventricle are brought into requisition,  when this kind of serosity is of too gross a nature, as it would naturally be when the cerebrum labours under certain affections or diseases, and when is thus threatens to clog up the avenues, that is, the various foramina in the system of the lateral ventricles. “

“That the cerebellar or cerebro-spinal liquid, under certain conditions, mixes with the cerebro or ventricular liquid which contains the elements of the white lymphatic blood, follows from this general position of Swedenborg's theory of the cerebro-spinal liquid; namely, that the various lymphs and serosities which pass under this name are all contained in the first place in the red blood, and that they are derived thence through a resolution of the blood into its constituent elements, in the substance of the brain. As the cerebral and cerebellar liquids are thus derived from the same original source, they are able, under certain conditions, to be of assistance to each other, and thus to be commingled. “