CONTROL OF NORMAL BREATHING IN FISHES BY RECEPTORS LOCATED IN THE REGIONS OF THE GILLS AND INNERVATED BY THE IXTH AND XTH CRANIAL NERVES

Abstract

Different combinations of sectionings of the IXth and Xth cranial nerves just central to the gills were carried out on the brook trout. When the Xth nerve was unilaterally or bilaterally sectioned breathing continued approx. normal and was often followed by a gasping type of breathing before death. When the IXth or the IXth and Xth nerves were unilaterally sectioned breathing continued approx. normal. Death followed generally without gasping. When the IXth or the Xth nerves were bilaterally sectioned there was always cessation of all breathing. As a rule this was followed by a gasping type of breathing. From these observations it was concluded that the control of normal breathing in fishes is dominantly reflex, originating in receptors located in the regions of the gills and innervated by the IXth cranial nerves.