Fig. 3. The effects of progressive transection of the vagi on stroke volume in the pulmonary and systemic blood flows (_pul and _sys, respectively) as well as heart rate (f_H) in unanaesthetised rattlesnakes (Crotalus durissus). In the first series of experiments (A–C), the left vagus was transected before the right whereas this order was reversed in the second series, i.e. right vagus was transacted before the left vagus (D–F). Either route terminated in complete vagotomy. _sys was calculated as 3.3 x blood flow in the left aortic arch. N=6 in each of the two experimental protocols and data are presented as means ± s.e.m. Values that are significantly different from the resting undisturbed condition are marked with an asterisk.