Figure 5.

Contributions of different components of the cardiovascular system to rate of oxygen consumption in resting and flying pigeons (Columba livia). The values for cardiac output and oxygen contents of arterial and mixed venous blood in the resting birds support a rate of oxygen consumption of 0.8 mmol O₂ kg⁻¹ min⁻¹, which is represented by the area of the smaller (rest) quadrangle. The values for cardiac output and oxygen content of arterial mixed venous blood in flying birds support a rate of oxygen consumption of 13.8 mmol O₂ kg⁻¹ min⁻¹, which is 17 times that during rest and this is represented by the total area of the larger (flight) quadrangle. (Adapted from Peters et al. [32].)