On the Autonomic Nervous System of the Teleostean Fish Uranos copus scaber

Abstract

ABSTRACT The sympathetic ganglia of Uranoscopus resemble those of mammals in that they are connected with the spinal nerves by white rami consisting of medullated (pre-ganglionic) fibres, and grey rami of non-medullated (post-ganglionic) fibres. The sympathetic ganglia are connected together by a chain in which the medullated fibres may run forwards or backwards and may also cross in transverse commissures to the opposite chain. No sympathetic nerves to the heart were found. The cardiac nerves spring from the vagus and consist of medullated fibres. The gonads and the mesonephros and its derivatives (kidneys, urinary bladder) receive nerves only from the sympathetic system, with the exception of the sphincters round the external openings of the gonads and bladder which are innervated by branches of the spinal nerves. There is, on each side, only a single anterior splanchnic nerve from the sympathetic system to the gut; there is therefore nothing corresponding to the pelvic nerves (sacral parasympathetic outflow) of Tetrapods. The sympathetic chain extends into the head and bears sympathetic ganglia in connexion with the vagus, glossopharyngeus, facialis, and trigeminus nerves. The rami communicantes between these sympathetic ganglia and the cranial nerves consist almost entirely of non-medullated (post-ganglionic) fibres; the pre-ganglionic fibres for these ganglia run out in the white rami of the third and fourth spinal nerves and thence forwards in the sympathetic chain. The ciliary ganglion resembles that of mammals, receiving fibres from the trigeminal sympathetic ganglion (radix sympathica), profundus ganglion (radix sensoria) and oculomotor (radix brevis). The sympathetic fibres in the long and short ciliary nerves (though post-ganglionic) are medullated. There is a bundle of fibres running from the trigeminal sympathetic ganglion via the radix longa and radix brevis to the oculomotor nerve. There is a separate profundus ganglion in Uranoscopus from which a small nerve passes to join the trigeminus (portio ophthalmica profundi?) while larger branches run to the long and short ciliary nerves.