Fig. 5. Haemodynamic effects of blood volume alterations in South American rattlesnakes Crotalus durissus, as a function of mean circulatory filling pressure (MCFP) measured at each blood volume change. (A) P_sys, mean systemic blood pressure; (B) P_CV, central venous pressure; (C) fH, heart rate; (D) _pul, pulmonary cardiac output; (E) _sys, systemic cardiac output; (F) _tot, total cardiac output. Black symbols represent the untreated group and grey symbols represent the -blocked group. Triangles indicate control values at normal blood volume. Values are means ± S.E.M. (N=6 for each group). * indicates a significant difference relative to control values. indicates a significant difference between the two groups of snakes. (1 cm H₂O=0.098 kPa.)