Fig. 1. Mean (±s.e.m.) rates of instantaneous oxygen uptake (M_O2) from water and air, and in total, as a function of water P_O2 (P_wO2) in seven jeju. The black arrows show the point at which either propranolol (left arrow) or atropine (right arrow) was injected (see text for details). The labelled red horizontal lines denote the periods when data were analysed for the comparisons shown in Table 1.