Fig. 5. The effects on total ventilation (percentage change from the starting values) of graded hypoxia, hyperoxic hypercarbia, hyperoxia and injections of NaCN externally into the respiratory water. In each graph, the different groups are C, control; GD, gills denervated; GOD, gills and orobranchial cavity denervated; DC, decerebrate control; DGD, decerebrate, gills denervated; DGOD, decerebrate, gills and orobranchial cavity denervated. The data are shown as the mean + S.E.M. (N=8-12). Asterisks indicate indicates values that are significantly different from resting values for fish within that group under normoxic, normocapnic conditions (100 % value).