PLATE IX.
THE SYMPATHETIC NERVE OF THE SKATE.
(RAIA BATIS.)
ON each side of the superior part of the abdomen, at a short distance from the spine, the sympathetic nerve forms an unequal oblong ganglion of a red-ash colour; it gives off both large and very small nerves, having this appearance, to pass on the mesentery, communicate with branches of the par vagum, and accompany the mesenteric arteries to the viscera. Some filaments are distributed about the testicles, and others pass towards the aorta; but these are too soft to be satisfactorily traced to their precise terminations.
The large ganglion communicates by a semitransparent tissue with a small one—this with the next, and so on to some distance down the spine; it communicates by the same tissue with the par vagum, and the large nerves collected from the spinal chord, which resemble the axillary plexus of the higher classes. It may be a question whether this semitransparent tissue be nervous; but as it connects small ganglia with each other, and with the large one, but little doubt can be entertained respecting its true character, notwithstanding the nerves proceeding from the large ganglion to the viscera have a different appearance.
The sympathetic nerve of this creature must be formed almost entirely for the abdominal viscera, as similar ganglia have not yet been observed in any other part of the body. There is, indeed, a ganglion attached to a branch of the fifth, and placed underneath the skin of the lower jaw, near each angle of the mouth, but it is almost transparent, and corresponds more with that of the gustatory nerve in some of the mammalia.
