Fig. 7. Data tracings of venom pressure recorded from the fang tip of Naja nigricollis. Note that stimulation of the M. adductor mandibulae externus superficialis (AMES) simultaneously with the M. protractor pterygoideus (PP) produces greater venom pressure than when either is stimulated alone. This pattern holds whether the muscles are given twitch (A) or train (B) stimuli.