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autonomic nervous system of the ratfish Hydrolagus colliei Paul, Frank

Abstract

Young immature specimens of Hydrolagus colllei were fixed in various fixing fluids and stained with eosin and hematoxylin, Mallory's triple stain, Bodian's protargol, and Holmes' silver method. Gross dissections of the autonomic system were carried out with the use of osmium tetroxide and Nelson's "in toto" stain for nerves. The cranial autonomic system appears to be similar to that of other selachians, except for the peculiarities of the vagus. The four vagal ganglia are separated from one another; the visceral branch of the vagus sends a branch to the pregastric ganglion, and the remaining fibres supply the anterior portion of the digestive tube, the musculature of which is predominantly striated. The gastric ganglion is surrounded by a large mass of suprarenal tissue; together they are termed the axillary body. The heart receives only a vagal supply, the fibres of which are in the walls of the sinus venosus and auricles; no fibres make contact with the ventricles. The sympathetic ganglia are, as a rule, segmentally arranged. The fibres connecting the ganglia are not organized into a definite trunk as found in higher vertebrates, but seem to course at random between the ganglia. Associated with the sympathetic ganglia are the suprarenal bodies, which are limited to the abdominal cavity. The anterior portion of the kidneys appears segmented; posteriorly they fuse and are not segmented. The interrenal body is situated in the centre of the fused kidney. There is no autonomic supply to the interrenal. The sacral outflow from the spinal cord is absent as it is in all fish. The lateral line branch of the vagus extends into the tip of the tail; it sends fibres laterally to the open lateral line canal. There is no sympathetic supply to the tail region, as the sympathetic system ends with the kidney in the posterior projection of the abdomen.

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