STUDIES ON THE VISCERAL NERVOUS SYSTEM

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Abstract
Adequate stimulation of the abdominal viscera of barbitalized dogs reflexly influences both the reflex and the tonus activity of the vasomotor center. Various stimuli applied to different organs produce in some dogs depressor and in others pressor responses. The factors which determine whether the response shall be pressor or depressor have not been determined. The splanchnic area always responded by vasoconstriction and the limbs by vasodilatation. The blood pressure may be determined by the resultant of the two, the heart rate remaining constant. By chilling the animal, a pressor could be converted into a depressor reflex. This phenomenon was reversible if the chilling was not too prolonged, otherwise it was persistent. The pressor-depressor reversal is not due to cooling the afferent arc of the reflex as in the Reid Hunt sciatic experiment. The pressor-depressor reversal is not related to "shock," as there was not time for a dehydration of the blood; there was vasoconstriction of the splanchnic area and never vasodilatation; the heart rate remained unaltered; the blood pressure did not fall except during the period of visceral stimulation. The tonus of the vasomotor center in barbitalized dogs maintains a very uniform blood pressure level. Visceral stimulation frequently produced large Traube-Hering waves which persisted 15 min. to 2 hrs.

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