The Elicitation of Viscero-motor Reflexes.

The elicitation of viscero-motor reflex especially from the small intestine has been studied on the cat under light barbituric anesthesia or after decapitation. On animals with good reflex irritability, the reflex can be elicited from the intestinal wall by mechanical, electrical, chemical and thermal stimuli without the involvement of the mesentery or of its connection with the intestine. The effect of a stimulation of the intestinal wall is stronger the nearer the stimulus is placed to the mesenterial connection. This is explained by the fact that the densityof the nerve fibres must be greater here. A cutano-motor reflex is much stronger than a viscero-motor reflex elicited by the same stimulus on an equal area of skin resp. intestinal wall. No basis has appeared for the assumption that the intestinal wall should be supplied with pain nerve end-organs, especially adapted for stretching or pulling, or which in any way should differ from the pain nerve end-organs in the somatic innervated tissues. The principle difference between the visceral and somatic innervated organs probably is a quantitative, the density of riociceptive nerve fibres with end-organs.