Fig. 4. The effects of progressive transection of the vagi on stroke volume in the pulmonary and systemic circulations (V_s,pul and V_s,sys, respectively) in unanaesthetised rattlesnakes (Crotalus durissus). In the first series of experiments (A,B), the left vagus was transected before the right whereas this order was reversed in the second series (C,D). Either route terminated in complete vagotomy. V_s,sys is calculated as 3.3 x stroke volume in the left aortic arch. N=6 in each of the two experimental protocols and data are presented as mean ± s.e.m. Values that are significantly different from the resting undisturbed condition are marked with an asterisk.