ON THE SPINAL PARASYMPATHETIC. PHYSIOLOGICAL SIGNIFICANCE OF THE SPINAL PARASYMPATHETIC SYSTEM IN RELATION TO THE DIGESTIVE TRACT

¹ Medical Clinic, Imperial University, Tokyo

1. The vagus supply to the stomach includes, besides parasympathetic fibres, a great number of sympathetic fibres. Some of the sympathetic fibres exert an inhibitory influence upon its peristalsis. The parasympathetic fibres in the vagus are distributed all over the stomach, but they especially supply abundantly the cardia and fundus region.

2. The number of parasympathetic fibres which run to the intestine varies according to the individual animal; thus in one they amounted to 119, and in another there were only 13. It follows that the grade and region of innervation must show individual differences.

3. The greater splanchnic contains, besides the well-known inhibitory fibres, many spinal parasympathetic excitatory fibres, coming from the dorsal roots of the thoracic segments. Their excitatory action is disclosed when the inhibitory fibres are interrupted by the application of nicotine to the cliac ganglion. The spinal parasympathetic fibres supply not only the intestine but the stomach, especially its pyloric region. In the dog, the left splanchnic supplies more fibres to the stomach than the right, the right supplying only the pylorus. Both splanchnics have an excitatory action upon the intestine, after the sympathetic inhibitory fibres have been interrupted. The right splanchnic supplies especially the uppermost portion of the small intestine. In the cat, the greater splanchnic acts more effectively upon the stomach than in the dog.

4. The spinal parasympathetic fibres supply the intestine segmentally through the lumbar sympathetic trunk. Their excitatory action may be greater than the inhibitory action of the sympathetic fibres, so that stimulation of the lumbar sympathetic trunk without nicotine application is enough to provoke contraction and peristalsis of the corresponding region of the intestine. The lower part of the lumbar sympathetic trunk (4th and 5th ganglion) innervates the first portion of the large intestine. Stimulation of this part of the lumbar sympathetic causes contraction of the large intestine. Section of all rami communicantes results in relaxation of the small intestine and of the upper part of the large intestine, but not of the uppermost part of the small intestine.

Nicotine application to the ganglia of the sympathetic trunk is followed by contraction and increased peristalsis of the small intestine (with the exception of its uppermost part); the upper part of the large intestine being also involved.