Fig. 7. A comparison of hepatocyte respiration in birds and mammals. (A) An allometric plot of the hepatocyte respiration rates (HRR) for different-sized birds (broken line) compared to the relationships (solid lines) previously described for mammals (from Porter and Brand, 1995) and ectotherms (from Hulbert et al., 2002a). (B) The composition of hepatocyte respiration for two birds (zebra finch and emu) and two mammals (mouse and horse). (Bi) The absolute values (in nmol O₂ mg^–1 dry mass min^–1) for these four species; (Bii) the relative composition for the same species.