Fig. 5. The allometric relationship between the amount of the respiration rate of hepatocytes (HRR) devoted to four subcellular activities and body mass of different-sized birds. The subcellular activities are: mitochondrial ATP production (A), mitochondrial proton leak (B), non-mitochondrial oxygen consumption (C), and the activity of the Na⁺ pump (D). Values are means ± S.E.M. N=4 for all bird species except for geese (N=3) and sparrows (N=2), and (in B only) starlings (N=3) and finches (N=2).