6. Echo

6. Echo.6. Die Echo.

Already the nerve that moves the tongue and the glossopharyngeal nerve, but most of all the vocal nerve, to which in the living body the function of the voice and of loud speaking belongs, stand, by structure, branching and organic purpose, in the closest relation with a part of the nervous system which, over against the nerves of the brain and spinal cord, forms a whole existing for itself, independent. This so-called sympathetic system, rich in ganglia and plexuses, from which all the viscera of the cavities of the chest and abdomen and the blood vessels of the whole body receive their nerves, does not spring, as the older view would have it, from the fifth and sixth pairs of nerves of the brain, but merely stands in connection with these, as with some other cerebral nerves and all the spinal nerves; and that supposed root would stand, already in respect of its uncommon fineness, in no proportion with the rest of its course.^* Therefore in the less perfect animal kingdom, and even still in malformations of the more perfect,^** a ganglionic system is found even without brain and spinal cord, and not seldom single connecting links are missing, without harm, in the chain of nerve knots of the sympathetic nerve from the brain downwards. With a particular clarity Reil^* has set out the relation which obtains between the ganglionic and the cerebral system. Already in structure the nerves springing from the brain and spinal cord differ strikingly from those of the ganglionic system, and from the vocal nerve, which belongs almost entirely to it. The latter are softer, more gelatinous, grey-yellow and reddish in colour, interrupted by frequent ganglia and plexuses, and cannot be resolved into fibres so easily as the whiter, harder, more strongly oxidized nerves of the cerebral system. While the nerves of brain and spinal cord, as good conductors, lead not only sensation to the brain but also the will from it to the parts, the nerves of the ganglionic system obey the will not: the movements of the blood vessels and of the intestinal canal are involuntary in the normal state, and a living animal opened up, which at once cries out when it is stimulated at a nerve springing from the cerebral system (the crural nerve, for example), endures stabs and cuts in a soft nerve of the ganglionic system without showing any pain. The whole vegetative system of the body, all those organs which work for the formation, preservation and growth of the material organism, belong to the field of the ganglionic system; and this, together with the vocal nerve, forms not only the plexuses of the throat, heart, lungs, diaphragm, mesentery, pelvis and of the preparation of the seed, but from that united system alone the great arteries receive their nerves, while the nerves of the cerebral system merely run along the blood vessels without branching into them. With the arteries, from whose content all the parts of the body form and maintain themselves, the nerves of the ganglionic system spread into all the organs, and there preside over all the processes of secretion, of material formation and of begetting.

* Sömmerring, Vom Bau des menschlichen Körpers, vol. V, div. 1, p. 322.